3 firefighters in critical condition after responding to building explosion in Dallas

DALLAS, Texas (KTRK) -- Three Dallas firefighters are in critical condition after an apartment building explosion Wednesday morning.

The firefighters were responding to a report of a natural gas leak at the apartment building when the explosion happened.

Officials said a total of seven people were hurt, three of which were civilians. They are expected to be OK.

Residents claim they knew there was an issue for a few hours before the blast.

"We are aware of what residents are reporting, that there was a gas smell that originated as early as last night, that seemed to be surrounding. Seemed to have taken place after an incident that the police department responded to," said Jason Evans with the Dallas Fire-Rescue Department.

The explosion caused most of the building to collapse, which sparked a fire.

Investigators were still on the scene trying to determine what may have caused the incident.