Mechanical problems triggered a fire aboard a bus in Panama's capital killing at least 18 people, injuring 17 and sending passengers jumping from the flaming vehicle, police said.
Investigators using trained dogs found no evidence of explosives on the city bus and believed some form of fuel leak was to blame for blaze. The bus lacked an emergency exit.
"We found absolutely no trace of the presence of explosives," said Jaime Jacome, director of Panama City's Technical Judicial Police. "What there was a lot of gasoline."
Witnesses said they saw smoke pouring from the area around the motor seconds before the bus caught fire.
Authorities were checking the charred remains of the motor and bus for clues.
Many passengers were seen scrambling to get off before flames engulfed the bus. At least 17 people managed to escape but all were hospitalised with severe burns.