In the end, five firefighters were hurt and seven people are out of their homes.
Firefighters say a ruptured gas line at the front door of a home in the Castro made the firefight very tough. 3 homes damaged. pic.twitter.com/pCIsbA1ryX— Amy Hollyfield (@amyhollyfield) October 20, 2016
Crews are still on the scene hours later to make sure there are no more flames or gas ruptures.
Investigators are now working to determine the cause. They believe it started in the garage but there's so much damaged debris to sift through, it could take a while to figure out exactly what started it.
The fire was huge and could be seen from several blocks away. That caused some confusion for firefighters as they tried to find it.
Fire investigators are focusing on the garage this morning where they think an overnight fire started that damaged 3 homes in the Castro pic.twitter.com/JAmPGmDQCW— Amy Hollyfield (@amyhollyfield) October 20, 2016
They were given three different locations from callers to 911, but once they found it on Hattie Street at Market, they knew it was a big one.
They called for a fourth alarm.
One of the major problems greeted them at the front door. "The gas line was ruptured right where we enter into the building, the front door there. There was a lot of fire throughout the building at that point so they had trouble making entry into the building," SFFD Batt. Chief Paul Crawford said.
Witnesses say that just when they thought it was dying down, the gas-fed fire kept roaring.
"I went to my rooftop and then I saw this huge fire coming from this side and then I stayed and watched for about another 10 minutes. Whenever I thought the flame had gone out and then it got worse. The flames just started getting really, really bad," witness Yen Phan said.
PG&E crews are trying to stop a small gas leak at scene of a house fire in the Castro. Fire melted one of their valves, causing the leak. pic.twitter.com/aJ7Bh6rzRs— Amy Hollyfield (@amyhollyfield) October 20, 2016
Five adults and two children had to run out of their burning homes around 12:15 a.m. Thursday. Three homes were damaged but everyone made it out OK.
The fire burned for a while. "We initially saw some low flames but they billowed and flared up very, very quickly. The flames went very high very quickly and they lasted for about an hour," witness Marion Delaney said.
There is glass and debris all over the sidewalk on Hattie St. in SF's Castro from a huge fire overnight. FF's think it started in a garage. pic.twitter.com/MnwloA6E8I— Amy Hollyfield (@amyhollyfield) October 20, 2016
About 100 firefighters responded to the scene and five were hurt.
"There was one severe injury. One of our firefighter paramedics was fighting the fire and fell over, caught himself and broke his wrist pretty bad. The rest were all minor injuries - cuts, bruises," SFFD Batt. Chief Charles Crane said.
As neighbors stop by to look at the damage, they just can't believe the destruction here and just what a total loss of these total homes. One on the corner was a historical building.
As far as the gas main problems, firefighters say it's pretty common for a fire to melt and burn systems that go in and out of a home.
They have all of the gas leaks capped and are trying to figure out what role this played in the cause of the fire.