A semitrailer truck turning at Alt. U.S. 19 and Martin Luther King Jr. Drive jackknifed about 4 p.m. Tuesday, spilling about 30 gallons of gasoline and snarling traffic for hours. Police re-routed motorists onto side streets while a crew cleaned up the spill during rush hour. No one was seriously injured in the accident and no other cars were involved, said Fire Marshal Rick Butcher. But it made a mess. Firefighters from the Tarpon Springs Fire Department sprayed foam on the gasoline to prevent the fumes from becoming a hazard and evacuated nearby convenience stores and small restaurants as a precaution. The truck had T&B Housemovers of Clearwater painted on its side. The company could not be reached for comment.