Equipment malfunction and human error are among the possible causes of a series of explosions which sparked a massive fireball at a central Florida propane plant and left eight people injured.

But Tavares Fire Chief Richard Keith said sabotage was not suspected.

The federal Occupational Safety and Health Administration launched an investigation into Monday's incident at the Blue Rhino propane plant in a town north-west of Orlando, as did the Florida State Fire Marshal's office.

No-one was killed, but eight employees were injured, four of them seriously. The injured include a worker who was hit by a car on a nearby road while fleeing the explosions.