A Philadelphia firefighter died after a Saturday morning fire led to a building collapse, trapping six people under the rubble, fire officials said.

The firefighter, a 27-year veteran of the department, was pronounced dead at the scene of the fire, the Philadelphia Police Department said in a Twitter statement. Fire officials did not immediately identify the firefighter who died.

“It’s a sad day for the Philadelphia Fire Department,” Craig Murphy, 1st Deputy Fire Commissioner, said at a Saturday news conference. “Unfortunately, our department lost a member bravely fighting a fire and caught in a building collapse.”

Fire crews responded to the fire at a commercial building around 2 a.m. Saturday, Murphy said. What initially appeared to be a “pretty routine fire” progressed into a “total collapse” of the building by around 3:30 a.m., he said.

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Six people – a building inspector and five firefighters – were trapped in the building during the collapse, Murphy said.

Four of the firefighters and the inspector were taken to a hospital, and the inspector has since been released, he said. Murphy said he does not know the exact status of the four firefighters who remain hospitalized but said they all appear to be in stable condition.

Murphy described the collapse as a “lean-to/pancake collapse” with a lot of “void spaces” where people could have been trapped. Authorities are currently investigating the cause of the fire and collapse, he said.

One person jumped from the second floor of the building to avoid being trapped, Murphy said. Others were speaking with rescuers and tapping on debris to help crews identify where they were.