By Ellen Wulfhorst

NEW YORK (Reuters) - Two people were reportedly missing on Friday in the wake of an apparent gas explosion that destroyed four New York apartment buildings and injured 19 people, police said.

The blast Thursday afternoon shook Manhattan's East Village neighborhood, causing two buildings to collapse and burst into flames. Two adjacent buildings caught fire as well.

Bloodied victims ran from the damaged buildings, and frantic residents climbed down fire escapes, helped by passersby as flames shot high into the sky.

The blast appeared to have been gas-related, New York Mayor Bill de Blasio said at a news conference. Private gas and plumbing work had been going on in one of the buildings, and Con Edison utility inspectors on the scene an hour earlier had determined the work was not satisfactory.

Two people have been apparently missing since the blast.

"We are looking into two individuals who are apparently unaccounted for, said a spokeswoman for the New York Police Department.

One of those was identified in local media as Nicholas Figueroa, 23, whose family said he had been eating lunch with a co-worker in a sushi restaurant where the explosion appeared to have originated.

His family told The New York Times that a bank statement showed he had used a debit card to pay $13.04 to Sushi Park.

Figueroa has not been heard from, his family said. His co-worker was hospitalized with injuries.

Firefighters were searching through the building rubble that was still burning on Friday morning, said a spokesman for the Fire Department of New York.

"We're putting out smoldering debris," he said.

Of the 19 people injured, four were critical, officials said. Two suffered burns to their airways, fire officials said.

The four buildings comprised some 49 apartments, leaving residents homeless, officials said.

Con Edison said its inspectors had evaluated a gas service upgrade being installed by a plumber in the building that later exploded and collapsed. The work failed inspection for several reasons, including that there was insufficient space for installation of a meter in the basement, it said.

Con Ed and city officials said there had been no reports of gas odors ahead of the explosion and that a survey of the main gas pipes on the block found no leaks.

The blast came little over a year after a gas explosion caused two apartments buildings to collapse in East Harlem, killing eight people and injuring dozens of others.

(Editing by Susan Heavey)