Investigators say someone intentionally set fire to the law library on the third floor of the Henry County Courthouse in Mount Pleasant overnight. Damage to the library is extensive.Witnesses spotted smoke coming from the courthouse about three A.M. Mount Pleasant firefighters extinguished the flames quickly and found someone had stacked up several law books and set them on fire. Fire damage was contained to the two rooms of the law library but several other areas of the courthouse were damaged by smoke. The courthouse is closed while the investigation and cleanup are underway. The courthouse, built in 1914, had caught on fire in the 1920s with moderate damage.