KOLKATA: Airports across the country were put on high alert after a hijack threat was made by an anonymous caller to the Air India office in Kolkata on Saturday. “Air India biman hijack kora hobe (Air India aircraft will be hijacked),” a male voice spoke in Bengali, triggering a security shake-up that included putting armed marshals on some flights.Kolkata Police’s Special Task Force and detective department are jointly trying to track down the caller. Security agencies are taking it very seriously as the threat has come at a time of heightened tension — Kolkata port was on alert in November last year and only two days ago, a suspicious vessel from Pakistan blew up after being challenged by the Coast Guard in the Arabian Sea.According to airport sources, the call came at AI’s city booking office on Central Avenue at 5.42pm, sparking a series of phone calls up the chain as senior airport officials and the home ministry were alerted. The Bureau of Civil Aviation Security (BCAS) immediately ordered airports across the country to strengthen security. The National Security Guard is being kept in the loop and sky marshals have been deployed on aircraft.Confirming the call, an AI spokesperson said the airline had acted promptly and informed all agencies concerned. “We have filed a complaint at Bowbazar police station. Since the threat was a general one, regarding AI flights, we have heightened security on all aircraft operating across the country,” he said.At Kolkata airport, an emergency meeting was convened at the anti-hijacking room in the air traffic management building to review security protocols and put in place additional measures to foil any threat. “More security personnel have been deployed in and around the airport. There will be tighter screening of people and anyone who appears suspicious will be detained and questioned. In addition, there are quick reaction teams on standby,” a source said.Plainclothes personnel were deployed at the terminal to spot suspicious activity among passengers and visitors. Security was tightened at screening points even for airport and allied staff. “Frisking and X-ray checks are always thorough but there are instances when the security officer uses his or her discretion to allow spices or pickles. Following the alert, there will be no allowances. To ensure that passengers do not carry anything unwarranted into the aircraft, secondary ladder point check has been enforced,” said an official.CISF has intensified screening of airline staff — including cleaners and securitymen — allowed into the apron area. Deliveries made by catering units to planes will also be checked with hand-held metal detectors to eliminate the possibility of someone smuggling arms or explosives.The additional checks led to slight delays in flight departures but with security top priority, no one complained.This is the second countrywide alert in recent times that has its genesis in Kolkata. In October, airports across the country were similarly cautioned after Airports Authority of India got a letter in Kolkata that warned of terror attacks by suicide bombers on Air India flights at Ahmedabad, Mumbai and Kochi.