Three Fort Worth firefighters were injured while fighting a house fire Monday afternoon.

Fire crews responded to multiple reports of a blaze in the 1200 block of East Cannon Street, just southeast of downtown Fort Worth, at about 6 p.m.

Eighteen units, including five engines and one medic unit, were dispatched to the scene.

Upon arrival, they found heavy fire showing from the left side and the second story of the home. Firefighters entered the home and made it to the second floor when conditions rapidly deteriorated, prompting the incident commander to call for an evacuation and declare a mayday situation.

Two firefighters bailed out through a second-story window, and a third reportedly fell through the roof, according to a social media account that posts first responder scanner traffic. All three firefighters sustained injuries and were transported to Parkland Hospital. One of the firefighters is listed in serious condition, while the other two are said to be stable, Fox 4 KDFW reported.

“This is something where we know there’s always the chance,” said Craig Trojacek, public information officer for the Fort Worth Fire Department, per CBS News Texas. “When the tones go off at a station, and we’re not sure if there’s anybody inside, we’ll do whatever we’ve got to do to get in there and make sure we’ve got everybody out safely, even if it’s putting ourselves in harm’s way.”

The sole occupant of the home was able to get out safely, but the structure suffered extensive damage.

“It can be pretty bad, that’s why I give it up to these guys with the fire department; they did a hell of a job for sure,” said neighbor Michael Barron, per CBS.

The cause of the fire is still under investigation.