A crew working in the basement area of an Ohio building intentionally cut a gas line not knowing it was pressurized before a deadly explosion this week, the National Transportation Safety Board said Friday.

The crew was there to clear out piping, outdated infrastructure and debris out of the basement in anticipation of a city project that would replace the sidewalks, CBS-affiliate WKBN reported.

Workers told NTSB investigators that they didn’t smell gas earlier in the day as they were working.

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NTSB Board member Chapman said this shows there was not a slow, ongoing leak.

Chapman said the workers didn’t know the line in question was pressurized or contained gas.

The explosion happened six minutes after crews cut the line, Chapman said.

As News Center 7 previously reported seven people were taken to the hospital after the explosion.

Akil Drake, 27, an employee of the Chase Bank branch in the building, was found dead.

NTSB is leading the investigation into the explosion.