The oil and gas appliances and several gas meters are now at the state fire marshal's office in Stow, where investigators are deciding which pieces need further scrutiny, spokeswoman Jennifer Mieth said.

"Now comes the rather boring, slow process of examining the evidence and figuring out whether anything needs to be tested," she said.

The fatal explosion at 65 Main St. claimed the lives of young sisters Iris and Violet Carey. Ten others, including the girls' parents, Heath and Tara Carey, escaped with minor injuries, but lost their homes.

Besides appliances and gas meters, evidence also includes gas lines and pipes, Mieth said.

"They're focusing on a possible gas explosion," she said. "They took anything that might have possibly been a source of a gas leak into the home."

Tony Defreitas, who crawled out of the home with his pregnant wife and son, said his last gas bill was more than $20 above normal for no reason. Heath Carey said NStar was at the home just a few months ago when the family's hot water heater was not working.

Town officials said oil was used to heat the home and gas was used for other purposes.

A 911 tape released yesterday could provide some more clues into what caused the devastating blast.

Janet Webster called 911 from her cell phone outside of the four-family home at 1:41 a.m., seconds before it blew up, authorities said.

"There's a terrible noise coming from my basement and it smells like gas really bad," she told the state police dispatcher who picked up the call and routed her to the Hopkinton Fire Department, just 50 yards away.

It could be weeks before investigators discover and release the official cause of the explosion, Mieth said.

Crews finished clearing the site of the blast by 2 p.m. yesterday and NStar officials arrived to inspect the area. The cleanup included a visit from Zecco Inc. of Northborough, which specializes in hazardous waste removal. Oil spilled onto the remains of the house when workers hit an oil line with a front-end loader on Wednesday, Fire Chief Gary Daughtery said.

Firefighters covered the hole with a plastic tarp and filled it with sand and pieces of the building's foundation.

"Our part of the investigation is pretty much done," Daughtery said.

The crater in the ground is littered with life's remains, including part of a dusty Barbie roller skate, broken CDs, crumpled photographs and high-heels.

Families who lived in the home lost almost everything. Crews brought anything that appeared intact to a Westborough salvage yard, where families can claim their belongings.

One of the few things that survived the explosion was a black and white photograph of Tara Carey's grandmother as a baby, family friend Nancy Hause said. Its frame destroyed, the photograph was pulled from the wreckage and kept at the police station.

Just a few feet away at the edge of the curb sits a growing memorial to the little girls who perished in the rubble. "Forever in our hearts" was written on the back of a purple Rhino that also bears the little girls' names.

Residents of Hopkinton and surrounding towns, many with their young children in tow, pulled up alongside the memorial under a tree yesterday and deposited flowers and poems.

"I feel really bad for them," 15-year-old Joyce Alexander said moments after contributing an original poem to the pile.

"I hope the families of Iris, Violet know that in a small town people are crying a lot," reads the last line of Alexander's poem.

Defreitas' wife, Poliana Compos, was due to give birth Wednesday. The 20-year-old was treated at MetroWest Medical Center in Framingham and released yesterday afternoon, still pregnant, authorities said. The family is staying in a hotel thanks to the American Red Cross.