A longtime Los Angeles City firefighter, who was approaching retirement, is fighting to survive after suffering injuries while battling a house fire in the Hollywood Hills.

The firefighter, a 38-year-veteran, was rushed to Cedars-Sinai Medical Center in grave condition. He was one of several firefighters trying to douse a fire at a huge home on the 1500 block of North Viewsite Drive. He remained in grave condition Thursday.

The fire broke out around 11:20 p.m. Wednesday. While crews focused on the roof, they were surprised to learn that the ceiling was full of water.

"The pipe to the sprinkler system actually melted, filling the ceiling up with water. Due to the nature of the construction, that ceiling was then saturated with water," said Los Angeles Fire Department Capt. Jaime Moore.

It was so much water that it collapsed all at once. A total of six firefighters were injured when the ceiling went down. Three of the firefighters are in fair condition, two with back pain and one with a broken ankle. Two county firefighters had minor injuries.

"It is very rare for an entire ceiling to collapse the way it did," said Moore.

Los Angeles Mayor Antonio Villaraigosa visited the hospital and released a statement, saying, "These first responders are real-life, everyday heroes who rush into the face of danger not just because it is their job, but because their devotion to the noblest of professions soars high."

The home has been red-tagged. Two people were inside the home when the fire started. They were able to get out safely before the firefighters even arrived.

"We had been sleeping. We don't know where it actually started. We just got awake by the sprinkler system," said homeowner Gerhard Becker.

The mansion was to be used as a location in the reality show "Germany's Next Top Model," starring Heidi Klum. More than a dozen models were supposed to have moved in by next week. But now those plans are on hold.

The cause of the fire was under investigation. Officials said they do not suspect that arson was involved.