The fatal explosion that brought on the collapse of a pair of New York City apartment buildings on Wednesday morning is now at the center of a federal investigation.

“We are operating under the assumption at this point that it is a natural gas leak that led to an explosion,” said Robert Sumwalt, a member of the National Transportation Safety Board.

The gas explosion, which is blamed for at least eight deaths and dozens of injuries, is something that unfortunately cannot be closely examined by authorities just yet.

That will require access to the Upper East Side neighborhood’s main gas pipe. As the rubble is still smoldering, fire officials continue to consider it a safety hazard.

Sumwalt said that once firefighters give the word that it’s safe, investigators intend to conduct a pressure test. The test is expected to pinpoint the source of the gas leak that led to the powerful explosion.

Residents in the area had reportedly complained to the Con Edison utility about the faint odor of gas for days ahead of the explosion, including the early morning hours before tragedy struck.

🙁 RT @WHAS11: NATIONAL: Eighth body found in New York City building explosion http://t.co/UQUiPwaftf

— Brokey McPoverty (@brokeymcpoverty) March 14, 2014

Deadly New York Explosion Highlights Urgent Need To Fix City's Crumbling Gas … – Huffington Post http://t.co/Ww5oaAYH7F

— New York Watch (@NewYorkWatch) March 15, 2014

Following the explosion, a devastating collapse followed. The event took the lives of eight individuals, Only four of the deceased have had their identities released to the public: Griselde Camacho, 44, Carmen Tanco, 67, Rosaura Hernandez, 21, and Andreas Panagopoulos, 43.

New York mayor Bill de Blasio said that 40 injuries thus far have been blamed on the explosion.

Some individuals are alleged to remain unaccounted for, raising speculation that there will be more bodies found among the rubble.

While much of the damage was heavily concentrated at the two collapsed apartment buildings located at East 116th Street and Park Avenue, several other nearby buildings are said to have lost heat and gas services in the aftermath of the explosion.

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