A massive gas line explosion took place at New York City's F. Kennedy High School on Thursday night, leaving three men severely injured. According to authorities, the New York City gas line explosion also caused heavy damage to three floors of the high school.

Firefighter said the blast occurred exactly 8:09 p.m. at the campus located in Terrace View Ave., Marble Hill.

"It was a thunder, a really loud explosion," said 21-year-old Addae Hicks, a custodian who was on at the campus' sixth floor at the time. "You could smell a lot of gas. I thought the building was about to go off."

According to police, the three severely injured workers from the New York City gas line explosion were among seven people doing construction work at the sixth floor's science laboratory after 8 p.m. The workers were reportedly draining gas from a main inside the lab. Because they failed to drain it completely, the blast occurred.

Apart from the injuries, the New York City gas line explosion also blew out windows on the floor and shook an apartment building nearby. Witnesses confirmed the damage while police said other heavily damaged floors include the fourth, fifth and sixth floors of the high school's building. Police also said that no fire took place following the massive blast.

Officials confirmed the three injured workers to be male and that they have been rushed to the Jacobi Medical Center in the Bronx. By late Thursday, one remained in critical condition, while the two others' conditions remained serious.

One of the workers was a 36-year-old man who suffered severe burns and covered his body. The two other workers, aged 38 and 35, both suffered burns on their hands and bodies.

"Searches are underway and continuing" for others who may have been injured during the New York City gas line explosion, according to a city official. It remains unknown whether the four other workers present at the explosion have been injured too.

According to the New York Times, over 140 firefighters and fire trucks arrived at the scene.

The JFK campus, which previously served almost 1,300 students in grades 9-12, now has eight specialty schools which serves 4,000 students, according to USA Today.

According to the city mayor, only after further investigation has been completed will officials know whether school openings are affected by the latest New York City gas line explosion.

The massive blast is the second largest gas-related explosion recorded this year. The last one to occur was in March when an East Village fire took place after another gas-related blast. The incident took the lives of 2 people and injured 25 others, reported The New York Daily News.