U.S. investigates Ohio building explosion [Video]

The U.S. National Transportation Safety Board is now leading the investigation into a massive explosion that blew out much of the ground floor of an apartment building in Ohio this week, killing a bank employee and injuring several other people.

The NTSB said pipeline and hazardous materials investigators arrived in Youngstown on Wednesday night, and would announce more details at a news briefing on Thursday.

Police and emergency officials initially blamed natural gas, but the fire chief later said the cause remained under investigation.

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“We have no idea what caused the explosion. We know that there was an explosion and it did a lot of damage to the bottom of the building,” Youngstown Fire Chief Barry Finley said.

The explosion shook downtown Youngstown around 2:45 p.m. Tuesday, collapsing part of the ground floor of …