NEW DELHI, July 14 (Reuters) - A preliminary investigation into the crash of an Air India passenger jet last month that killed 260 people raises additional questions about the incident and the investigation is far from over, Air India's CEO said in a memo on Monday.

Campbell Wilson told staff in a memo that the pilots had passed a mandatory preflight breathalyzer test.

The investigation report says Air India did not carry out those inspections - prompting speculation that the accident could have been caused by faulty switches being flipped by accident. However, in an internal note seen by the BBC, the FAA has since reiterated its belief that the issue did not compromise safety.

Experts says only few people were well-versed with the aviation industry to tell fake from genuine information, and debunk wildly speculative hypotheses.