MEXICO CITY—Mexico’s state-owned oil company said Monday that a bizarre chain of events, including a lightning storm and a simultaneous gas pipeline leak, set off a strange subaquatic fireball seen last week in the Gulf of Mexico. Petroleos Mexicanos said an intense storm of rain and lightning on July 2 forced the company to shut off pumping stations serving the offshore rig near where the fire occurred. Simultaneously, the leak in an underwater pipeline allowed natural gas to build up on the ocean floor and once it rose to the surface, it was probably ignited by a lightning bolt, the company said. Pemex sent fire control boats to pump more water over the flames and no one was injured in the incident in the offshore Ku-Maloob-Zaap field. It said no crude oil was spilled. Pemex said it was repairing the pumps and investigating the cause of the gas leak. The …