Around 600 sky lanterns were seized from shops and houses in Bangur and Rajarhat on Kali Puja on Sunday.

Sky lanterns are banned within a 10km-radius of the airport as they pose a threat to flights. Police in Bidhannagar had issued a notification in the run-up to Kali Puja and Diwali banning sky lanterns and laser shows because of difficulties faced by pilots.

Lanterns appear harmless as they soar up in the air but can cause plane accidents if they get sucked into the engine of an aircraft, according to the notification. Also, they can trigger fires as they fall to the ground in flames.

Teams from New Town, Rajarhat, Lake Town and Baguiati police stations raided shops and houses in their areas and seized the lanterns and banned firecrackers.

The largest haul was at Rajarhat, where cops found 300 sky lanterns and 1,500 banned firecrackers in a shop, the police said.

“The team had raided the shop based on specific information,” Kunal Agarwal, deputy commissioner (headquarters), Bidhannagar City Police, said. “Sky lanterns are a threat to aircraft safety. If they land on the airport premises where oil companies store highly inflammable aviation turbine fuel, the results could be catastrophic.”

The police seized more than 40 sky lanterns near a housing complex in Bangur. “A team approached a group of people gathered in front of the housing complex… they were firing lanterns and taking photographs on their phones and cameras. We told them that lanterns were banned,” another officer said. “They appeared surprised… we seized the lanterns and let them off with a warning.”

In New Town, too, cops seized over 250 sky lanterns.

The notification was issued after the North 24-Parganas district administration received a letter from the general manager of air traffic management in Calcutta on the threat posed by lanterns. The letter spoke of laser shows and how they affect pilots.

The police had conducted awareness drives across Baguiati, Rajarhat and Narayanpur. The inspectors-in-charge of six police stations in the Bidhannagar commissionerate’s Airport division had been asked to spread the word on the ban, the officer said.

Debanjana Das, an atmospheric scientist with George Mason University in the US, said sky lanterns polluted the air though their smoke emission was low. “They emit little smoke but anything burning in the air is harmful.”