NTSB investigating after deadly explosion rocks downtown Youngstown, Ohio

The National Transportation Safety Board said Wednesday it is investigating a deadly natural gas explosion that rocked downtown Youngstown, Ohio.

The explosion occurred near Central Square on Tuesday afternoon, police said, as they urged people to avoid the area.

One person was killed and seven people injured -- including one critically -- in the explosion, officials said.

It is unclear what caused the blast, which impacted a building that contains a Chase bank and apartments, Youngstown Fire Chief Barry Finley said.

The NTSB said its team of pipeline and hazardous materials investigators is arriving in Youngstown on Wednesday to investigate the natural gas explosion.

The Ohio State Fire Marshal is also investigating what caused the explosion, police said. A large perimeter was set up around the blast site on Wednesday as officials continued their investigation.

The body of a man who was an employee of the bank -- identified as Akil Drake -- was recovered from the basement early Wednesday morning, officials said.

"It's a tough part when you have to tell a mother that her son got up yesterday to go to work and he did not come home," Youngstown Mayor Jamael Tito Brown told reporters during a press briefing on Wednesday.

Drake was a 2015 graduate of Penn Hills High School in Pittsburgh, Pennsylvania, where he played football, the school district said. He was a graduate of Youngstown State University, school officials confirmed to ABC Youngstown affiliate WYTV.

Mercy Health said Tuesday evening it is treating seven people who were injured in the incident, including one person in critical condition. The critical patient remained in intensive care on Wednesday, officials said during a midday press briefing.

The Chase Bank is located on the ground floor of the building, with apartment units on the 12 floors above. The floor collapsed into the basement, which was flooded, officials said.

The building and a neighboring hotel have closed and streets in the surrounding area are shut off to traffic indefinitely due to the potential for structural collapse, authorities said.

A Chase spokesperson told ABC News the company is in "close contact with local officials to check on the safety of everyone in the building and area."

"After that, we'll work to determine what happened and to assess the damage," the spokesperson said.

There is no evidence of any suspicious activity at this time, officials said.