Eight people were injured, including four firefighters, after what is believed to be a gas explosion Wednesday morning at a Dallas apartment building. Investigators are still determining the cause for the explosion.

Firefighters responded to a 911 call about “a strong smell of gas,” around 10:20 a.m. CT, Dallas Fire-Rescue spokesperson Jason Evans told a local Dallas news station. Residents reportedly said they had smelled gas for about 12 hours.

Evans stated that the crew immediately responded to investigate the gas leak. He said it was when they were close to pinpointing the location of the gas leak when the worst happened.

“At some point during the course of investigating the odor, an explosion occurred; causing a partial collapse of the two-story apartment building,” Evans said in a statement.

A resident in a neighboring building told the Dallas Morning News that he saw a firefighter exit with his clothes on fire. Another resident described the scene as something out of a "scary movie."

The explosion left three of the firefighters in a critical state. One firefighter was in a stable condition who was released from the hospital. The four residents of the apartment are listed as stable.

One building a part of the multi-building two-story apartment complex was shown completely collapsed. Debris from the explosion was also blown to various parts of other surrounding apartments and a nearby parking lot.