AVALON — Three people injured when their house exploded, caught fire and collapsed told investigators they were working on a water line in the kitchen and noticed a funny smell just before the blast.

"They were doing some water line repair or valve replacement in the kitchen area and, at some time during that, they have this odor appear in the house and they're not really sure what it is," said deputy Allegheny County fire marshal Don Brucker.

Authorities planned to return to the ruins in the Pittsburgh suburb on Wednesday after thunderstorms and nightfall halted their investigation Tuesday before a cause could be determined.

Columbia Gas, which provides utility service in the area, found no evidence of a leak or stray pocket of natural gas underground, company spokesman Matt Pitzarella said.

Authorities did not immediately release the names of the woman and two men inside the home when the blast occurred Tuesday about 2:40 p.m.

Neighbors reported feeling the explosion up to two blocks away.

A spokeswoman at Mercy Hospital in Pittsburgh confirmed three victims were being treated there, but could not immediately provide other information. The hospital is well-known for its burn treatment unit.