Four thefts in three days have sent alarm bells ringing loud and clear through the high-security corridors of Netaji Subhas Chandra Bose International Airport.

Preliminary investigations have revealed that goons posing as ‘visitors’ are infiltrating the domestic terminal and targeting luggage and valuables of travellers. They are said to be hand-in-glove with some officials and trolley-boys on the inside, as they go about their ‘job’ with quiet efficiency.

Additional superintendent of police, North 24-Parganas, Ajay Nand, confirmed on Sunday that “four thefts of baggage and other valuables” had been reported over the past three days.

Nand attended a meeting last Friday to review the security situation at the airport. Police officers manning the airport said they had evidence of a nexus among criminals, a section of airport officials and staff operating in the domestic terminal.

The police suspect the recent thefts to be the handiwork of a gang of five goons, who enter the domestic terminal with visitors’ tickets and keep a track of the luggage movement and disposal system, besides targeting passenger lapses. Alleging that a section of trolley-boys acted as conduits, airport officials said they often helped unsuspecting passengers with their luggage and either disappeared with it or extorted money.

“Our initial findings suggest that these criminals from neighbouring areas cannot carry out their operations without support from within the airport,” said Nand.

“We realise the gravity of the situation. So many innocent passengers are being robbed. We have proposed a ban on the entry of visitors. We have also stepped up vigil in front the terminal building,” he added.

A rickshaw-stand near the domestic terminal was also cleared on Sunday.

Complaints registered with the airport police station over the past three days reveal how passengers have fallen prey to the racket inside the domestic terminal.

On December 26, Ashis Banerjee, a passenger bound for Delhi, was waiting near the “security check’’ gate with a luggage-laden trolley. He spotted a friend and started chatting. A couple of minutes later, he turned to take his trolley, but by then it had disappeared.

“Then, a courier company filed an FIR saying cellular phones and cameras had been stolen from a packet inside the terminal building,’’ Nand said.

A couple of days earlier, a trolley-boy, Narayan, stole the luggage of an elderly woman passenger. She lodged a complaint with the police and was forced to board the aircraft without her luggage. The police said Narayan was later arrested.

Another passenger, B.B. Biswas of Salt Lake, has registered a complaint that her daughter’s purse went missing in the airport. Police said Biswas’ daughter had kept the purse in a bag, which went in for security check. When the bag came back to her, the purse was not there.

“We have told the police that if they have evidence of any airport employee being involved with criminals harassing passengers, they should be immediately arrested,” said an official of the Airports Authority of India (AAI).

But Roshan Lal, director, AAI, chose to describe the recent thefts as “isolated incidents.” Maintaining that it would not be possible to accept the police suggestion to ban visitors into the domestic terminal, Lal said the Centre had taken a decision to allow people to enter the airport with a ticket.

“We cannot stop that,’’ said Lal. “There maybe some bad elements in the crowd but it is for the law-and-order force to identify and arrest the culprits.”

S.S. Kirpekar, inspector-general of the Central Industrial Security Force (CISF), responsible for guarding the airport, claimed “the incidents (of theft) have been blown out of proportion.’’