A gas leak caused an explosion and started fire in a propane boiler of a printing press (500 people). Two employees sustained burns, including one who sustained second degree burns and was transported to the hospital by a helicopter. One employee was unwell due to the fumes released. The leak results from the rupture of a propane supply pipe that passes through the far end of the equipment room near the quick cut-off and control element regulated from the outside by a palm button. An error in operating the power lift truck to move the wooden pellets piled up in front of the pipe may be the cause of the leak. The boiler was supplied by a 35,000 kg tank of liquefied propane.