Police are still looking for two people unaccounted for on Friday after a gas explosion and fire that injured 19 people in New York City and caused apartment buildings to collapse.

The two people have yet to be found after the explosion in Manhattan's East Village Thursday, Reuters reports.

A few building caught fire after the explosion and two collapsed down to rubble as fire fighters extinguished the flames.  

New York Mayor Bill de Blasio said the explosion occurred because of private gas and plumbing work that was going on in one of the buildings.

Just an hour before the blast shook the East Village, Con Edison utility inspectors said the plumbing work was not satisfactory.

Two buildings are now a pile of bricks, steel and broken glass among rubble that once were items that belonged to the tenants.

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

News outlets identified one of the missing persons as Nicholas Figueroa who has not been heard from since the blast.

The 23-year-old was eating lunch with a co-worker at a sushi restaurant where the explosion took place. Figueroa's co-worker has been hospitalized with injuries but still no word from him.

Four buildings in the East Village were destroyed because of the blast. Two completely collapsed, one mostly collapsed and will have to be razed while another caught fire and had a lot of damage.

The gas service upgrade installed an hour before the explosion failed inspection because there was not enough space for installation of a meter in the basement, according to Con Edison.

Fire fighters combated the flames for hours before the buildings completely collapsed, The New York Times reports. More than 250 fire fighters responded to the call.

There were 19 people injured in the chaos about four of them were critically injured, and four of them were fire fighters with minor injuries.