The cab of a semitractor-trailer caught fire Wednesday evening as it crossed the Bill Emerson Memorial Bridge into Missouri. Just after 5 o’clock scanner traffic indicated the truck was on fire on the bridge. The Cape Girardeau Fire Department went to the scene just west of the Highway 74/Fountain Street intersection with one ladder and two engines. The fire was extinguished within minutes. All lanes were open as of 6:45 p.m. Capt. Quentin Gaither of the Cape Girardeau Fire Department said no one was injured in the fire. Gaither said the fire is believed to have been caused by an engine malfunction. A more specific cause has not yet been determined.