NEW YORK (CBSNewYork) — Mayor Bill de Blasio on Thursday said the evidence pointed to a gas explosion in the blast that destroyed several buildings in the East Village – even though there were no reports of odors or leaks.

As CBS2’s Weijia Jiang reported, the mayor said initial indications suggested a plumbing crew may have triggered the blast in 121 Second Ave. All but the façade of that building ended up collapsing, and neighboring 123 Second Ave. completely collapsed.

The building to the south at 119 Second Ave. also partially collapsed. All three buildings were completely gone by 11 p.m., and neighboring 125 Second Ave. sustained major fire damage.

“Preliminary evidence suggests gas-related explosion. That investigation is ongoing,” the mayor said at a news conference Thursday evening. “The initial impact appears to have been caused by plumbing and gas work that was occurring inside 121 Second Avenue.”

But Con Edison said there were no reports of gas odors in the area before the explosion, and on Wednesday, a survey of gas mains on the block found no leaks.

Just one hour before the blast, Con Edison inspectors were in Sushi Park restaurant on the ground floor of 121 Second Ave.

Con Edison President Craig Ivey said crews from the utility company were evaluating the installation of a meter for new gas service at the building earlier Thursday. The building already had gas service, but was upgrading to a larger service. The new installation did not pass inspection and was not ready for gas to be introduced, Ivey said.

“The work failed our inspection for several reasons, including insufficient spacing for the installation of the meter in the basement,” a statement from the utility company reads. “A survey conducted yesterday of the gas mains on the block found no leaks. We continue to work with all agencies on the investigation into the cause, and we are praying for the recovery of all the injured.”

Carlos Torres, the vice president of emergency management for Con Ed, spoke exclusively to CBS2 investigative producer John Doyle about the private contractor doing the work to install the new gas system.

Torres: “There was no leak. There was no leak at the time we were there.”

CBS2: “But you were there to inspect the pipes?”

Torres: “The new piping.”

CBS2: “The Japanese restaurant had installed these pipes.”

Torres: “I guess the plumber for the Japanese restaurant.”

CBS2: “And your guys said, ‘This is no good,’ so what happens next?”

Torres: “Nothing, Nothing changed the status of the piping, and we left. We did what had to be done. We took pictures, and what we do is we go back and explain to them why they didn’t inspect.”

Con Edison said the work failed the inspection partly because the space for a new gas meter was not big enough.

The 121 Second Ave. building dates back to 1886, according to city documents.

PHOTOS: Second Avenue Building Explosion

It was unclear which private contractor was involved in the gas meter work. Workers could supply many answers about what happened, but it is believed to be likely that they are among the seriously hurt.

De Blasio emphasized the importance of contacting authorities if they smell gas.

“If people smell gas, they should immediately call 911 or Con Edison,” de Blasio said. “That’s the one thing we know for sure.”

A building explosion in Harlem in March 2014 was caused by a faulty gas line.