Four firefighters were injured while responding to the scene.
A Dallas apartment building partially collapsed after firefighters were called in to investigate a carbon monoxide leak, according to authorities.
When firefighters arrived at the South Dallas apartment building around 10:30 a.m. local time, they noticed a smell of gas around the building, according to Dallas Fire-Rescue.
An explosion occurred while fire crews were investigating the scene, causing the two-story building to partially collapse, authorities said.
The fire was producing flames and dense smoke at 11 a.m., Dallas Fire-Rescue spokesman Jason Evans told reporters at a news conference Wednesday afternoon. At least half of the building appeared to be badly damaged and piles of building debris could be seen scattered around the structure.
“The damage is extensive,” Evans said. “The collapse itself is extensive.”
Seven people, including at least four firefighters, were injured in the blast and were taken to local hospitals. Two victims are in critical condition; five are in stable condition, according to Dallas Fire-Rescue.
Residents began reporting the smell of gas Tuesday night, Evans said. It did not elaborate on the initial investigation into those reports.
It is not clear what caused the explosion, fire officials said. No additional information was immediately available.
James Scholz of ABC News contributed to this report.