By Niluksi Koswanage
KUALA LUMPUR, March 9 (Reuters) - Malaysian officials are poring over CCTV footage and questioning immigration officers and guards at Kuala Lumpur's international airport, concerned that a security breach may be connected to the disappearance of Malaysia Airlines flight MH370.
Suspicions that the Beijing-bound Boeing jet, which vanished on Saturday with 239 people on board, may have been hijacked or bombed have risen after at least two passengers were found to be using stolen passports, though Malaysia's government stressed it was considering all possibilities.
Malaysian investigators, assisted by the FBI, are probing the identities of four passengers in particular, two Malaysian officials with knowledge of the investigation told Reuters.
The four comprise two travellers with European passports, possibly Ukrainian, in addition to two travelling on stolen Austrian and Italian passports, the sources said.
"We have deployed our investigators to look through all the security camera footage. Also, they are interviewing immigration officials who let the imposters through," said one official with direct knowledge of the investigation.
"Early indications show some sort of a security lapse, but I cannot say any further right now."
The head of Malaysia's civil aviation authority told reporters on Sunday that two "imposters" had been identified by investigators as they made their way from check-in, through immigration to the departure gate. Malaysia's transport minister, Hishamuddin Hussein, confirmed that investigators were looking at four passengers.
A spokesperson for Malaysia Airports Holdings, which operates the country's airports, declined to comment.
Malaysian Prime Minister Najib Razak said on Sunday that the country's airport security protocols would be reviewed, The Star newspaper reported.
Asked how strongly investigators suspected foul play, the second official said: "There are initial indications but it's too early ... who knows what happened on that plane. But we are keeping our minds open."
UIGHUR LINK "NOT RULED OUT"
The timing of the incident, a week after knife-wielding assailants killed at least 29 people at a train station in the southwestern Chinese city of Kunming, led to speculation that militants from China's Uighur Muslim minority could be involved.
One of the Malaysian officials said the authorities were not ruling out Uighur involvement in the jet's disappearance, noting that Uighurs were deported to China from Malaysia in 2011 and 2012 for carrying false passports.
"This is not being ruled out. We have sent back Uighurs who had false passports before. It is too early to say whether there is a link," the official said.