A fire that swept through the main building of an elementary school was caused by arson, according to officials who are also investigating anti-Semitic slogans discovered after the blaze was extinguished.
The fire began Nov. 22 just outside the Gardner Academy's main building, fire officials said.
However, no details were released about what led investigators to conclude that the blaze was arson.
School officials said they had no evidence or other reasons to suggest that students were involved in the incident.
City officials are offering a $5,000 reward for information leading to an arrest and conviction in the case.
The school had just completed a $4.5-million renovation, but the project did not include a sprinkler system.
Unlike most buildings, public schools are not required to have sprinkler systems because of the expense, said Rick Carruth, an arson investigator for the San Jose Fire Department.
Although schools install smoke alarms and take other precautions, Carruth said, "They're exempt because of the cost of installing sprinkler systems. Their attitude is that most schools aren't occupied when they burn, so they're willing to risk the possible property loss."
The investigator said he couldn't recall any instances in which students died because they were trapped by a fire.
Meanwhile, a police sergeant said, once the fire was extinguished, swastikas and anti-Semitic phrases were found scrawled on the walls.
"We're investigating it as a possible hate crime," said San Jose Police Sgt. Steve Dixon. "We're looking for the culprit. Whether this person and the one that started the fire are one in the same, we're trying to find that out."
The federal Bureau of Alcohol, Tobacco, Firearms and Explosives, the FBI and San Jose fire and police departments have worked on the investigation.
The fire destroyed much of the 22,000-square-foot main building, which included the administrative office, the library, computer labs and seven classrooms. Other campus buildings sustained smoke and water damage.
The San Jose Unified School District plans to tear down the remnants of the main building and begin construction on a new building by summer. Most of the rebuilding will be covered by insurance, a fire official said.
According to a recording Friday, the school's 460 students and 28 teachers will continue to be bused to two local schools, Horace Mann Academy and Ernesto Galarza Elementary School.
Associated Press contributed to this report.