A massive explosion ripped through the heart of downtown Youngstown on Tuesday afternoon, injuring six people and leaving one missing.

Initial reports suggest a gas leak may be to blame for the devastating incident. Witnesses described hearing a loud boom followed by thick smoke billowing from the Chase Bank building, located on the ground floor of the Realty Building.

Eyewitnesses, including Debora Flora, executive director of Mahoning County Land Bank, described the scene with harrowing clarity.

"I heard the boom, and I could see dark smoke coming out of the side of the Chase Bank building… but it was such a really strong, strong boom," Flora told WKBN.

Security camera footage from a neighboring business captured the terrifying moment the explosion ripped through the structure, shattering windows and sending debris flying.

WFMJ reported:

Chase Bank occupies the first floor of the building, but the 13-story building also houses numerous apartments.

The neighboring apartment building International Towers is being evacuated for safety.

People are being evacuated from the building and all occupants and news crews have been ordered to move to the Market Street Bridge.

About seven people have been taken to the hospital and one person is still considered missing, Youngstown Fire crews are working to locate them now, according to Youngstown Fire Chief Barry Finely.

Finley says an evacuation order has been issued for everyone 365 degrees around the building. We're also told everyone in the building has been accounted for.