Grass and waste are being set on fire regularly on empty plots in New Town, forcing residents to stay indoors and keep their doors and windows shut as dense smoke engulfs entire blocks.

On Wednesday, residents of DF Block in Action Area I were greeted with an acrid smell of burning grass and plastic and dense white smoke.

A few residents stepped out to locate the source of the smoke. Bhujaya Roy Choudhury, one of the residents in the group, said they were shocked to see mounds of what seemed to be a mix of dried grass and plastic on fire.

“The smoke was so bad that our eyes started hurting and it became difficult to breathe,” Roy Choudhury said.

The residents alerted police.

Soumyosree Dasgupta, a resident of a housing complex in Action Area II, said people were lighting fire on the field behind their complex almost every other day. Residents and guards of the complex tried in vain to catch the people who are doing so.

New Town does not have an air quality monitoring station and there is no way to measure the impact of the fires on air. The air quality index in neighbouring Salt Lake, which has a monitoring station, was 284 on Wednesday, which is considered poor.

“Since it is biomass burning, it will release PM2.5 and PM10. The impact on the air will depend on the existing pollution in the area,” said Anumita Roy Chowdhury, the executive director of the Delhi-based Centre for Science and Environment.

The impact, she said, will not be limited to New Town. “Burning of stubble far away from Delhi worsens the air quality of the city. It depends on the wind speed and direction…. The same will happen in New Town and Calcutta, too,” she said.

An official of the New Town Kolkata Development Authority (NKDA) said they, too, failed to catch anyone responsible for lighting the fires. He said they had come to know that the fires were being lit for various reasons, including clearing undergrowth and scaring away snakes.

NKDA chairman Debashis Sen said they had placed notices on vacant plots asking people not to light a fire. A meeting has been scheduled with the pollution control board on Friday.