Select members of the cleaning staff will be Calcutta airport security's eyes and ears inside washrooms in a bid to stop gold smuggling.

Security officers have realised that smuggled gold bars often change hands in the washrooms, away from the prying eyes of CCTV cameras.

At least two employees hired by private agencies engaged for various airport services have been arrested after stepping out of washrooms with gold bars. There are more than 700 surveillance cameras across the terminal and the parking lots, but washrooms provide the privacy that smugglers and their conduits seek.

"It is illegal to install CCTV cameras in washrooms. So we have asked the supervisors of the two contracted cleaning agencies to ask their trusted workers to keep an eye. If they notice any suspicious movement, they are required to report it immediately to the CISF or customs," an airport official said.

Since the CISF can't spare manpower to guard the washrooms, trusted cleaning staff are the best bet, the official said.

Employees working at the airport know that most parts of the terminal, apron area and even the car park zone are under CCTV surveillance. The integrated terminal has 45 washrooms but security agencies say the ones most likely to be misused are those in the arrival lounges.

A source in the CISF said their personnel had already been asked to increase vigil outside the washrooms. "But it's not possible for our staff to find out what is happening inside a washroom. The cleaners can do the job of unobtrusive surveillance for us."

On March 10, an employee of a private agency was arrested with gold bars worth Rs 37.65 lakh. The accused, 29-year-old Arun Kumar Behuria, had allegedly concealed the gold bars in his innerwear. Behuria was not on duty when he was arrested.

Customs officials suspect a passenger handed him the bars to get them out of the airport.

Gold smuggling increased after a hike in import duty in August 2013. A passenger now has to pay 10 per cent of the value of imported gold as customs duty and three per cent as cess, which works out to almost Rs 3 lakh a kilo. Earlier, the import duty on gold was Rs 22,000 a kilo.

Several passengers have been caught over the last two years bringing gold concealed in LCD/LED TVs and torches, among other things. Some even take medical risks by hiding gold bars in their rectum.

Since vigilance was stepped up following the increase in import duty, gold smugglers became wary of employing the old tricks and started looking for ways to involve insiders who wouldn't be suspected of being in league with them.

Anyone working in the terminal or the airport area needs a pass issued by the Bureau of Civil Aviation Security (BCAS) on the basis of a background check, but it's far from foolproof. Since even a person with a clean background can be lured by money, a new rule is being implemented. "The time of duty will be mentioned in all passes. We have asked all private agencies to ensure that their employees submit their passes and exit the terminal once their duty hours are over," the official said.

The airport has been divided into around 12 zones and passes are issued for each. "An employee who has a pass for the arrival area won't be allowed to enter the departure level," the official said.