By Sebastien Malo and Laila Kearney

NEW YORK (Reuters) - Two bodies found on Sunday at the site of a gas explosion that destroyed three New York City apartment buildings last week, injuring 22 people, were believed to be those of two unaccounted for men, the city's top fire official said.

The bodies were found about 20 feet apart of one of the buildings reduced to rubble by the blast and fire in Manhattan's East Village neighborhood on Thursday, Fire Department Commissioner Daniel Nigro told reporters.

While Nigro said a medical examiner had not officially determined that the remains belonged to the two people who remain unaccounted for, local broadcaster NY1 News said one of the missing men, 23-year-old Nicholas Figueroa, had been identified by his family as one of the bodies found on Sunday. Also missing was Moises Lucon.

"Those were the two people that had been reported missing and we think we found those two," Nigro said, though he did not rule out the chance of a third victim. "The feeling is that everyone who had been reported missing has now been found."

Figueroa and Lucon were believed to be in a sushi restaurant in the building where the explosion occurred, New York Mayor Bill de Blasio has said. Lucon, 26, worked at the restaurant, according to NY1 News.

On Sunday, rescue workers could be seen digging through the rubble backed by cranes hoisting debris and a front loader pushing twisted metal and bits of furniture into a pile on a street. Rescuers had been using used cadaver dogs to search for victims.

At a nearby restaurant, Local 92, a sign read: "Our hearts [are] with people who got hurt and lost their homes."

In all, three buildings collapsed out of four that caught fire, and 11 buildings were evacuated, leaving residents of 144 apartments homeless.

Investigators were looking into whether gas and plumbing work being done privately in one building led to the explosion, and utility Con Edison said that its utility crew found dangerous gas line connections that created a "hazardous situation" during a visit in August prompted by the smell of gas in the basement.

The utility said it shut off the building's gas for about 10 days, until it was determined to be safe.

The basement could hold the key to the cause of the devastation, police said. On Friday, de Blasio said the blast was possibly tied to someone inappropriately tapping into a gas line.

Nigro also said workers had not reached the basement of the building and authorities had not reached any conclusions about the cause of the blast.

An hour before the blast Con Edison inspectors had been at the scene and determined that pre-existing work was not satisfactory, but the problems were not safety-related, de Blasio said.

(Reporting by Sebastien Malo and laila Kearney in New York; Writing by Eric M. Johnson; Editing by Cynthia Johnston, Eric Walsh and Bernard Orr)