It was their younger daughter Iris' fifth birthday, and they came ready, with presents and balloons. They sang "Happy Birthday," then released two balloons, watching as they vanished into the June sky over the Vernon Grove Cemetery in Milford.

Iris and her older sister Violet, 5 1/2, died last year when a natural gas explosion ripped through their Hopkinton apartment building.

"We talk to them all the time," Tara Carey said of her daughters this week. "(We tell them) just that we miss them and we love them, and we pray they're together.

"I get worried about them still. It really hurts to know they're not here anymore."

Nearly a year after the explosion, the couple is still struggling with their loss and waiting for answers from state investigators probing the cause of the blast.

So far, those answers have been slow in coming.

Within days of the explosion, officials from the state fire marshal's office pulled evidence, natural gas pipes and fittings from the rubble at 65 Main St.

Months passed, however, before the state's utility regulator, the Department of Telecommunications and Energy turned the items over to West Boylston-based Massachusetts Materials Research Inc. for testing.

More long months passed as the testing, originally slated to take about a month, drew out over nearly six months.

With the testing now virtually complete, DTE Executive Director Timothy Shevlin said he expects to issue a report by the end of the summer.

"We understand (they are) in the process of completing their final report," he said of the testing company.

But the slow pace of the work has been maddening for the couple who saw their lives destroyed in an instant.

"That day we lost both our children, our house, our car was destroyed, our clothes -- we lost everything," Tara Carey said. "For us to say just take your time and we'll rebuild our lives..."

Heath picked up the thought as she trailed off. "...It's really frustrating because there's nothing we can do about it, just sit here and wait for them."

'Just a normal night'

When it started, July 24 seemed like any other day.

Violet spent the day with her best friend, Morgan, while Heath and Tara brought Iris to work with them. That night, the family ate dinner together, then the two girls hopped in the bath before heading to bed.

By about 11 p.m., Heath and Tara went to bed themselves, the four of them curled up together.

"The next thing we know is...we woke up to the explosion," Tara said. "There was an extremely loud noise, and then I remember falling."

At 1:41 a.m., a blast ripped through the apartment building, collapsing all three floors, and blowing out the windows of nearby buildings.

Heath Carey found himself sitting up, his back wedged against the bed, his legs covered in rubble.

"I could hear one of them (the girls) in front of me, and they were making...not-good sounds," he remembered. The girl -- he's still not sure if it was Violet or Iris -- was moaning and struggling to breathe.

Desperate to help, Heath worked his legs free, and quickly found Tara, but could not free either of the girls.

"It felt like it was a nightmare," Tara said. "The whole thing was just a big confusion. We didn't even know we were on the ground."

Firefighters pulled the couple from the rubble of the building, and shepherded them to the nearby police station while the search for Violet and Iris continued.

It was then, they say, a series of blunders, began that continues today.

Within hours, emergency workers pulled Iris from the rubble and rushed her to Milford-Whitinsville Regional Hospital. But it wasn't until some time later the message reached the girl's parents.

Wanting to be near their daughter, the couple were bundled into a police cruiser for the ride to the hospital.

But in a perplexing act of miscommunication, the couple were taken to MetroWest Medical Center in Framingham, not Milford-Whitinsville. By the time authorities realized the mistake, Iris had died.

Hours later, searchers located Violet, but instead of taking the girl's lifeless body to the hospital, she was taken directly to the morgue.

The first time they saw their oldest daughter's body, Tara and Heath said, was after an autopsy had been conducted.

"That's just how this whole year has seemed," Tara said.

The aftermath

In the days following the accident, the Careys struggled with their wrenching grief and the sad work of burying their daughters. Investigators combed through the wreckage, searching for clues that might hint at the cause of the blast.

But as state officials geared up for tests on evidence from the blast, the family, frustrated at being locked out of the process, asked a judge to force the state to allow their own experts to participate.

"We were told we were going to be actively involved in everything that happened," said John Wozniak, the Mendon attorney hired by the family. "The bottom line is in the initial stages we didn't know what the state fire marshal was doing."

At the center of the dispute was a "transition fitting," a pipe fitting that connects the gas line from the street to the house's gas system. The fitting was found, rusted and broken, among the debris.

State regulators wanted to glue the fitting back together, then pressurize the device to see if it would break or leak. The family objected to the test, saying it would destroy key evidence.

Though the testing finally went forward in January, the delays have the family frustrated.

"It'll be a year on July 24," an embittered Tara Carey said this week. "And we're sitting here, basically not any closer than we were the day after it happened.

"All we want to do is find out what happened, just like anyone else. That's all we're looking for. We didn't physically die that day, but our whole life died that day."

State officials, however, insist the testing was done as quickly as possible.

"We couldn't begin to conduct the real technical testing of the materials that were involved...until we had custody of it," DTE director Shevlin said. "We didn't actually get physical custody of these materials until November 2002."

The analysis, which includes metallurgical testing, examining parts using microscopes and X-rays, began in early January.

"(The testing is) basically to see if they can find any flaws," explained Robert Smallcomb, director of the DTE's Pipeline Engineering and Safety Division. "Anything that would lead to corrosion or other failures."

As expected, Smallcomb said, most attention was focused on the transition fitting. A final report from MMR Inc. should be published by the end of the month.

Based on that report, the DTE may recommend regulatory or safety changes in the way natural gas is handled. Those recommendation should be published by the end of the summer, Shevlin said.

Dealing with tragedy

Tara and Heath Carey say the memory of the July night is a raw wound.

"We still have nightmares about it," Heath admitted. "It took even a while to go to sleep at night."

From time to time, he said, he wakes up with a start in the middle of the night, and can again feel the heat of the explosion on his legs and the noise of the blast in his ears.

Following the explosion, the couple moved into Tara's mother's house in Milford, and slowly pieced their lives back together.

"We didn't even have our drivers' licenses, or our Social Security cards," she said. "We had to completely start over."

By December, they'd saved enough to move into an apartment in Milford, but their first night in their new home was heartbreaking.

"That was kind of the point where we just kind of realized this is permanent, forever," Heath said. "Here we are in an apartment just like we were before, except we don't have our two daughters."

The couple limped along in Milford for four months before deciding to relocate to Onset in April, where the family regularly vacationed in years past with Violet and Iris.

Earlier this year, though, a glimmer of hope appeared on the horizon.

Following the blast, Heath underwent surgery to reverse a vasectomy he had had following Iris's birth. Doctors gave the procedure a 30 percent chance of success.

In January, the good news arrived -- Tara was pregnant, this time with a boy they plan to name Lexington.

"He is our little miracle," Tara said. "We're really excited we'll be able to have more children. We can't wait to see him and hold him and love him."

But questions of what they'll tell their son about his sisters are clearly emotional ones.

After a long pause, Heath, holding back tears, seemed to shrug.

"I don't know," he said.

Tara says small things affect her deeply.