JOPLIN, Mo. (AP) -- Investigators say it will take a few days to determine if the fire that destroyed a southwest Missouri mosque was arson.

Michael Kaste, special agent in charge of the FBI's Kansas City office, said Monday that the agency is taking the investigation into the fire at the Islamic Society of Joplin very seriously. He says the FBI and the Bureau of Alcohol Tobacco and Firearms together have about 30 investigators working to determine the cause.

No injuries were reported.

Jasper County officials say patrols at the mosque had been stepped up since a July 4 fire at the mosque was determined to be arson. The FBI has released a video of a man appearing to set the July 4 fire and is offering a $15,000 reward in that case.