7 hurt, 3 critical in Dallas apartment building collapse

DALLAS, Texas — A Dallas apartment building partially collapsed Wednesday after firefighters were called to investigate a carbon monoxide leak, according to officials.

When firefighters arrived at the South Dallas apartment building around 10:30 a.m. local time, they noticed an odor of gas around the building, according to Dallas Fire-Rescue.

While fire crews were investigating the scene, an explosion occurred, causing the two-story building to partially collapse, officials said.

A fire caused by the explosion produced flames and heavy smoke, Dallas Fire-Rescue spokesman Jason Evans told reporters in a news conference. At least half of the building appeared to be badly damaged and piles of debris from the building could be seen strewn around the structure.

"The damage is extensive," Evans said. "The collapse itself is extensive."

Seven people, including four firefighters, were injured in the explosion and taken to local hospitals. Three firefighters were in critical condition; and the remaining victims are expected to be released from the hospital, according to Dallas Fire-Rescue.

Residents began reporting the smell of gas as early as Tuesday night, Evans said. He did not elaborate on the initial investigation into those reports.

It was unclear what caused the explosion, fire officials said.