Malaysia has investigated the possible suicide of the pilot on the Malaysia Airlines flight that went missing on March 8 with 239 passengers and crew on board.

Transport Minister Hishammuddin Hussein said that police have studied the crew members’ last days before the plane went missing and searched the residences of the pilot and co-pilot.

The police also probed the background of a passenger on board, aviation engineer Mohd Khairul Amri Selamat, a 29-year-old Malaysian citizen, the minister added.

Malaysia also asked all countries with citizens on board the missing plane to provide detailed profiles on the passengers.

Home Minister Zahid Hamidi affirmed Malaysia will reveal results of an investigation into the lost passports used by two Iranian passengers at an appropriate time.

The search area for the jetliner stretches from Australia to Kazakhstan. The Malaysian government sent diplomatic notes to all countries involved in the search and rescue operation.

On March 18, Chinese Ambassador to Malaysia Huang Huikang said that China has started to search along the north corridor of its territory.

Background checks on all passengers from the Chinese mainland did not find any evidence that they were linked to a hijacking or terrorist attack on the jet, he added.

Earlier on March 17, the armed forces of the United Arab Emirates (UAE) announced they will take part in the search with the involvement of two search and rescue aircraft, while New Zealand deployed aircraft P3 Orion to Australia to help the search in the Indian Ocean.

The US Navy's 7th Fleet announced on March 17 that the USS Kidd, an Arleigh Burke-class destroyer that has been searching in the Indian Ocean, will return to its normal duties. However, the US continued its mission in the broadened area in the southern Indian Ocean.

Flight MH370 lost radar contact on its way from Kuala Lumpur to Bejing on early March 8.-VNA