NYC Building Fire: 2 Unaccounted for, 22 People Injured in Explosion

— -- Two people were unaccounted for after a building explosion led to a seven-alarm fire in New York City on Thursday afternoon, according to city officials

A New York Police Department official identified one of those unaccounted for as Nicholas Figueroa, 23.

No information on the second person was immediately available.

At least 22 people were injured, four critically, after the fire in Manhattan's East Village, New York City Mayor Bill de Blasio said this afternoon. Earlier, city officials had said 25 were injured.

Figueroa's father, Nick Figueroa, told ABC News his son went to lunch in a restaurant at the bottom of the building that caught fire. He said he has had no contact with his son since the explosion and that investigators began searching for his son Thursday evening.

Neal Figueroa, Nicholas' brother, told ABC affiliate WABC this morning outside the Harlem apartment he shares with his brother that the family knows Nicholas Figueroa was at the Sushi Park restaurant because he has a pending charge for $13.04 at the establishment. The family last heard from him just before 2 p.m. ET, he said.

"Right now, we're just worried," he said.

Neal Figueroa said his brother was on a second date with a female co-worker that he hadn't yet met, but who he believed was in the hospital with numerous injuries following the explosion.

The family found out Nicholas Figueroa was missing when he didn't show up to work at Bowlmor Lanes at Chelsea Piers, he said. He was expected at 5 p.m. ET.

Neal Figueroa said the family has tried to locate Nicholas Figueroa through police, investigators and 311.

Neal Figueroa told WABC he was confident in his brother, referring to his brother as "Superman."

"I know he's strong enough to get out of this," he said.

It was unclear how many people were inside the building when the fire occurred, according to the New York City Fire Department. The incident took place in a bustling area with many restaurants and pedestrians, blocks away from New York University.

The FDNY confirmed that four buildings were affected and three buildings collapsed as a result of the fire and that firefighters were still putting water on some pockets of fire Friday morning. As of early this afternoon, firefighters had not started going through the rubble, city officials said.

"Once the debris is cleared and the fire is fully extinguished, then we will do a full investigation and clean-up," De Blasio said, adding that the full investigation "take days."

"Preliminary evidence suggests a gas-related explosion," DeBlasio said Thursday, adding that the investigation is ongoing. He said the incident "appears to have been caused by plumbing and gas work that occurred in 121 2nd Avenue."

De Blasio said today that it is rare to "see a scene of such devastation in a city like this."

"This was 24 hours ago a vibrant, bustling street," De Blasio said. "And today, people are dealing with the aftermath of this tragedy."

"The response by all of the first responders was exceptional," the mayor added, noting that the fire department arrived within minutes.

De Blasio said he saw "great acts of kindness and bravery" on Thursday, including an off-duty firefighter who climbed up a fire escaped and looked into apartments to see if anyone was home.

The four people in critical condition include two individuals with burns to their airways and another person who was unconscious following the event, according to FDNY Commissioner Daniel Nigro.

Of the about 250 firefighters who responded to the blaze, four were transported to area hospitals, where one was in fair condition, said the fire department. The conditions of the other firefighters weren't immediately released.

Around 3:17 p.m., witnesses reported what sounded like an explosion at Sushi Park restaurant at 121 2nd Avenue, which is at the bottom of a five-story, pre-war building that houses a handful of residential units.