By Madeleine Thomas
June 11 (Reuters) - A string of fires that have erupted mostly in unoccupied buildings across the central California city of Fresno this spring may be the work of serial arsonists, fire officials said on Wednesday.
Since May, more than 21 fires have occurred in Fresno, said Kirby Johns, a spokesperson for the Fresno Fire Department.
Johns declined to say how many arsonists officials believed could be at work, but said investigators suspect that they are located in three or four different parts of the city.
Most of the buildings had been unoccupied but a jewelry store was burned in downtown Fresno in early June. Two of the blazes have been three-alarm fires requiring more than 60 firefighters to combat the flames, Johns said.
"They're large fires in large, vacant buildings, so it requires a very large number of resources to mitigate those instances," he said. "Between two of those buildings, there was a million dollars in fire losses."
Johns said investigators were looking into the cause of the fires. The Fresno Bee newspaper reported that crews found evidence of a severed gas line left in the "on" position at one location.
Officials are also looking into the possibility that several fires that occurred before the recent string of blazes could be the work of the same arsonists. (Reporting by Madeleine Thomas; Editing by Dan Whitcomb and Will Dunham)