Secret tests on new engine emerge as possible cause of sub disaster

An analyst believes this explains why there were 15 extra people on board

The malfunctioning of a new type of diesel engine undergoing secret tests is the latest theory to emerge as a possible cause for the disaster that killed 70 aboard one of the country's submarines last month.

Hong Kong-based PLA expert Ma Ding-shing said that would explain other mysteries about the accident off the coast of Yantai city in Shandong, including the more than normal crew aboard the Ming Class No. 361 submarine.

'The 15 extra people on board, over and above the normal crew of 55, pointed to a team of observers developing a new engine that does not require an abundant supply of oxygen to burn diesel,' said Mr Ma.

The new technique, already developed by Sweden, Britain, Russia and the US, uses a chemical filter to take carbon out of carbon dioxide, leaving oxygen to burn, he said.

Another theory is that the engine simply malfunctioned. The Boston Globe reported that a mechanical failure had caused the main diesel engine to keep running when the submarine was submerged, suffocating the crew.

The newspaper cited 'a senior navy official' as saying the submarine had charged its batteries from its diesel engine on the surface before submerging. Diesel power is supposed to switch off when a submarine submerges because diesel needs oxygen to burn.