(CNN) -- An early morning fire that severely damaged the Texas governor's mansion in Austin may have been caused by arson, fire officials said Sunday.
Investigators "found evidence that the fire was intentionally set,'" said Texas State Fire Marshal Paul Maldonado.
Maldonado did not elaborate on what that evidence was, but said state and federal authorities would be searching for a suspect or suspects.
The mansion was empty because it was undergoing a multimillion-dollar renovation.
Firefighters were called out to the blaze at about 1:15 a.m., Austin Fire Department Division Chief Dawn Clopton said.
The fire shot through the building and made it too dangerous for firefighters to get to the second floor, Clopton said.
The mansion's roof partially collapsed.
The house has served as the official residence of Texas governors and their families since 1856, according to the governor's Web site. Watch fire fighters in action »
Firefighters kept the historical importance of the building in mind as they fought the blaze, Clopton said.
"We were as careful as we could be with the state of Texas' pride and joy," said Clopton. "We are trying to save as much of the structure as we possibly can."
Texas Gov. Rick Perry -- who is in Europe at an economic conference -- has been told about the fire, his spokeswoman Krista Piferrer said.
"It's a tragedy," she said. "It's a tragedy for the first family that has lived here since 2001. It's a tragedy for Texans and for all the governors that have come before us."