One of the engines of a Saudi Arabian jumbo jet exploded Tuesday while it was flying with 293 people from Manila to Riyadh, airport officials said. No one was injured in the accident. Airline officials, who were reluctant to give details, said the blast apparently resulted from a mechanical failure rather than sabotage. The state-owned Saudi Arabian Airlines jet was 20 minutes into the flight when the engine blew up. It safely returned to Manila. There were 276 passengers and 17 crewmen aboard.