NEW YORK (CBSNewYork) — Three people are dead and at least nine people are missing after a massive explosion rocked East Harlem Wednesday morning, leveling two buildings and sending smoke and flames billowing into the air.

At least 70 others were also injured in the blast, which happened at 9:31 a.m. Wednesday on Park Avenue at 116th Street, 1010 WINS reported.

While the FDNY only listed 27 injured patients, many others came to hospitals independently and were not treated by the department.

PHOTOS: Harlem Explosion

The explosion reduced two five-story buildings to rubble. It also shattered store windows for blocks and hurled glass, bricks and other debris throughout the neighborhood.

Witnesses Describe Blast Heard From Blocks Away

As CBS 2’s Andrea Grymes reported, cellphone video showed the flames and panic as people rushed to help. One woman was helped away barefoot, while another, whose car was hit, could be seen falling down while trying to get away from the scene.

The explosion and building collapses were so strong they even generated weak seismic signals that were recorded at seismographic stations in New York City, the Lamont-Doherty Earth Observatory said.

Click Here To View Seismic Records From Park Avenue Explosion And Building Collapse

Lamont-Doherty Cooperative Seismographic Network is a regional center for the Advanced National Seismic System.

The seismic waves were recorded at both the Central Park station and the Fordham University station in the Bronx at 9:31 a.m.

WATCH: Cell Phone Video Captures Moments After Blast

Witnesses said the explosion could be heard 40 blocks away.

“I came out, looked up and a building was just gone,” witness Mack Mayor said. “It’s just like a war zone out here.”

“Like a bomb, an explosion. Very loud. It scared the daylights out of me,” East Harlem resident Wilfredo Cruz told CBS 2’s Don Champion.

“I was sleeping in my bed and all of a sudden something blew up and the bed started shaking, the floor. And I said ‘what is this,’ I thought the world was coming to an end,” said East Harlem resident Robert Santiago.

“The smoke started to rise. It looked like something fell because it wasn’t like a fire. It just looked like debris smoke, similar to 9/11,” said witness Samuel Paul, who was on the 15th floor of a building on 125th Street.

Lashean Daniels, who lives next door to one of the buildings, told CBS 2’s Tracee Carrasco the blast ripped the wall out of her apartment and sent her running for her life.

“When we got downstairs we thought it was safe and it wasn’t. They started saying ‘run, run it’s going to explode again’ and people were running down the block. It was chaotic,” Daniels said.

Witness Jorge Perez says the impact sent another man near the buildings flying through the air.

“As soon as he stepped on sidewalk, that’s when it went boom! And I saw him flying,” Perez said.

And the haze from the smoke was so thick, rescuers and residents wore masks so they could breathe. Many people had to wear masks.

More than 250 firefighters responded to the scene. By 5 p.m. the flames were finally knocked down.

Victims Included Public Safety Officer, Dental Assistant; 9 Others Still Missing

One of the victims who was killed in the blast was identified as 44-year-old Sgt. Griselde Camacho by Hunter College, CBS 2 reported.

Asthma kept Camacho home from work on Wednesday, CBS 2’s Dave Carlin reported.

The college said Sgt. Camacho served as a public safety officer at Hunter since 2008 and worked in Silberman School of Social Work building.

“We are sad to report that, in an explosion that destroyed two buildings in East Harlem this morning, we have lost a member of the Hunter family….Our hearts go out to Griselde’s family at this terrible time,” Hunter College President Jennifer J. Raab said in a statement.

“We know this is a difficult time for all those who knew and worked with Sergeant Camacho, whether at the Silberman School or as part of the public safety office. All of you will be in our thoughts in the days ahead. We will update the community soon about plans to hold a memorial and about where to send your condolences,” the statement said.

A Facebook page has been set up in Camacho’s memory.

A second victim has been identified as Carmen Tanco, 67, who worked as a dental assistant. Both Tanco and Camacho lived at 1644 Park Ave. and were home at the time.

As CBS 2’s Dave Carlin reported, Tanco had every Wednesday off from her job, and relatives said that fact doomed her to die in the place she had called home for 40 years.

“It’s horrible,” said neighbor Maria Barretto. “It’s really horrific.”

Family members tried calling Tanco’s cellphone praying she’d left the apartment before the explosion.

“All my family has been trying to call her all day long, just hoping that, you know, maybe she’s in the neighborhood doing something; so running errands or something,” said Tanco’s niece, Lucina Ortiz.

The FDNY has not yet identified the last victim, who was said to be female, CBS 2 reported.

Meanwhile, the Mayor’s office said nine occupants of the building remain unaccounted for, according to Fire Marshals and the NYPD.

Searches of the street have been completed and did not produce any additional victims, the mayor’s office said.

“Our hearts go out to all the families involved,” de Blasio said at a news conference earlier Wednesday. “We are spending every effort to locate each and every loved one.”

Many families were in distress Wednesday night, including the Salas family, with a husband unaccounted for.

“Everybody knows each other from 5, 10, 20, 30 years ago,” Barretto said. “Everybody is praying for all these families.”

Of the dozens hurt and hospitalized, a 15-year-old boy being treated at Harlem Hospital Center was described as the most critically injured.

The boy suffered broken bones, internal injuries, and was seriously burned.

“He did verbalize some things when he first came in, but he was quite confused and severely injured,” said hospital chief of emergency Dr. Reynold Trowers.

A representative of Harlem Hospital Center said the hospital received 13 patients from the explosion. Three patients were children, including the 15-year-old boy in critical condition. The other two were in stable condition. The hospital said 10 adult patients, ranging in age from 20 to 79 years old, were treated and released.

A Metropolitan Hospital Center spokesperson said the hospital had received 19 patients related to building collapse. Six came by ambulance and eleven walked in on their own with minor complaints, the hospital said. All were treated and released.