New York City's Mayor has called the deadly explosion "a tragedy of the worst kind."
A police spokesperson confirmed Thursday that the death toll from the blast has risen to seven.
Over 70 people were also left injured after the two buildings collapsed in the city's East Harlem neighborhood.
Nearby structures were badly damaged by what witnesses say was a massive explosion.
"It blew out some of my windows, like in the back of the building. The whole courtyard has glass in it. And like, my apartment shook."
New York City Mayor Bill De Blasio spoke at an emergency press conference.
"There was a major explosion that destroyed two buildings. The explosion was based on a gas leak. The impact effected buildings around the two that were destroyed, very heavy impact on the surrounding buildings. A heavy fire has ensued as well."
A resident in an adjacent building reported smelling gas just 15 minutes prior to the blast.
Other people in the neighborhood have also told reporters they had smelled a gas-like odor since the day before.
Dozens of firefighters remain on site searching for any survivors who might be trapped under the debris.
De Blasio praised the city's fire department for its quick response, especially as there was no indication in time to save people.
President Barack Obama has sent his condolences to the victims' families.
Kwon Soa, Arirang News.