About 40 immigration officers are under investigation in what police believe is an "inside job" after the theft of three notebook computers at Chek Lap Kok airport that stored passport information on 3,000 suspicious travellers.
Initial checks suggested the theft was an inside job because access to the room that stored the three laptops was restricted, a police source said.
Only four teams of nine immigration officers had the keys, he said.
"The officers are required to lock the room with the key when they leave. Only officers with the key and their colleagues can enter the room," the source said. Cleaners and security guards did not have a key, "so we believe it is an inside job".
It was understood that the computers contained passport images of targeted dubious passengers in transit whose travel documents were scanned upon arrival.
The scanning procedure was aimed at preventing such visitors from using other identities to board another plane or revisit the city. The data was transferred to the department's server and deleted regularly if no further suspicions arose.
Another source said investigation would focus on two possibilities - whether the target of the theft was the computers or the data inside. He believed the computers had been sneaked out of the airport. "We are looking into all possibilities," he said.
Officers said it was difficult to get in touch with the 3,000 travellers as it was unknown whether the department had a spare copy of the data, which did not contain contact information.
The three laptops were understood to have cost about HK$15,000 each when they were bought in 2009, but are now estimated to be worth only several thousand dollars.
The devices were last seen plugged in and were being recharged on tables in the room on Tuesday night. It is understood that no other valuables are stored in this room.
The three computers were missing when a team of immigration officers arrived to work at about 7am on Wednesday. A police report was made the following day.
The room is situated inside the Immigration Department's duty office in the airport's restricted area, next to immigration counters in the arrival hall. The duty office is manned by several immigration officers around the clock.
It is believed that no surveillance cameras are installed inside the room or duty office. The New Territories South regional crime unit is checking surveillance footage of access points to the duty room and the airport's restricted area.
On Thursday, police interviewed 26 immigration officers in connection with the case. No one has been arrested and none of the laptops has been recovered.
A department spokesman said the case had been referred to the police and it would fully support the investigation.
Additional reporting by Niall Fraser