(Network Indiana) – Not every house or structure that was damaged or destroyed in Wednesday’s explosion in Evansville has been thoroughly searched by firefighters for people who might still be alive, said Fire Chief Mike Connelly, in a Thursday morning update with reporters.

Three people have been confirmed dead, and 39 houses damaged, with 11 of them uninhabitable.

Connelly said those homes would have to be demolished.

“Some of our guys were able to make an initial pass. In fire terms we do a primary search, a quick brief. But, a secondary search is thorough. So, we have not yet conducted secondary searches,” he said.

Connelly said for safety’s sake, his crews were not allowed to do those secondary searches.

“One of the things we have to do as incident commanders is ensure firefighter safety. So, we have to hold them back for their safety,” said Connelly.

He also said that the investigation into the cause would be a “tedious” process. The ATF was on the scene Wednesday doing a blast survey. When asked if he could rule out a gas explosion, Connelly would not budge on his position that the cause is as of yet, undetermined.

“I could speculate, but I’m not gonna speculate. The investigation’s underway. No cause determined.”

Connelly asked that if anyone has video of the explosion that they give it to the police, or to him so he can turn it over to the police “so that they can compile evidence that will assist in the investigation.”