By Barbara Goldberg

NEW YORK (Reuters) - Rescue crews with cadaver dogs clawed through smoldering rubble on Saturday in the search for two people still unaccounted for two days after an explosion destroyed three buildings in Manhattan, a spokesman for New York Mayor Bill de Blasio said.

Firefighters also digging their way toward the building basement where the explosion originated in the East Village used hoses on hot spots in the wreckage, said a spokesman for the Fire Department of New York.

The basement could hold the key to the cause of the devastation, which the mayor on Friday said was possibly tied to someone "inappropriately" tapping into a gas line. It could be a week of careful digging through twisted debris, bricks and splintered wood before the basement is reached, authorities said.

Twenty-two people were injured - four critically - in the explosion that completely destroyed three buildings and badly damaged a fourth, police said.

Two people still unaccounted for were in a sushi restaurant in the building where the explosion occurred. They were identified by police as Moises Lucon, age 27 or 28, and Nicholas Figueroa, 23. Figueroa is a college student who was eating lunch with a co-worker at the restaurant, his family told local media.

In all 11 buildings were evacuated, leaving residents of 144 apartments needing places to stay. Con-Ed said they may return to their homes as soon as Sunday.

Investigators were looking into whether gas and plumbing work being done privately in one building led to the explosion.

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

The contractor, identified as Dilber Kukic, was one of 50 people arrested in February in a sweep of the city by building and housing inspectors. He was accused of bribing an undercover investigator to dismiss violations at two properties, according to the Manhattan District Attorney's office. The hospitalized Kukic could not be reached for comment.

(Editing by Scott Malone and Greg Mahlich)