The report, by the state's Department of Telecommunications and Energy, could recommend regulatory or safety changes in the way natural gas is handled to avoid similar accidents.

In August, West Boylston-based Massachusetts Materials Research Inc., released a report on the cause of the July 2002 blast, saying testing on pipes and fittings pulled from the home did not cause the deadly gas leak.

The DTE's report is expected to build on MMR's conclusions, officials said earlier this summer. Director Timothy Shevlin was not available for comment on the report yesterday.

Officials are hoping to determine exactly what happened in July 2002, when an early-morning explosion ripped through a three-apartment building in downtown Hopkinton.

The blast leveled the building, injuring most residents and trapping Tara and Heath Carey, and the couple's two daughters, Violet, 5 1/2, and Iris, 4, in the rubble.

Rescue workers quickly pulled Tara and Heath Carey from the rubble, but the two girls did not survive.

In August, an attorney representing the parents of the two girls dismissed the report's findings, calling the tests fabricated and suggesting key evidence had been overlooked.

"After one year, we have a report that tells us nothing other than under these artificial conditions we have a part that didn't come apart," attorney John Wozniak said. "Nothing contained in the report surprised us in the least."

The family also filed a $50 million wrongful death suit against NStar gas, their landlord and Holden-based pipe fitting manufacturer Inner-Tite Corp., claiming a faulty natural gas fitting was behind the explosion. That case is pending.