A fire at a Kent business burned so hot early Friday that it partially collapsed the roof, according to Puget Sound Regional Fire Authority. Crews were called about 3:20 a.m. to the 24800 block of Pacific Highway South after an automatic fire alarm sounded. A police officer patrolling the area confirmed there was heavy smoke and flames. About 30 percent of the roof had already collapsed by the time firefighters arrived, which meant they sounded a second alarm in case the blaze spread to two nearby businesses.