Supporters of Trinamool Congress, which began the dharna on Sunday promising that it would be peaceful, allegedly threatened workers who turned up for work, forcing them to return, the police said.

On Wednesday, workers of an ancillary unit and a van-puller were assaulted allegedly by Trinamool supporters.

A Tata Motors spokesman said that attendance of the contract workers on Thursday is less than 15 per cent than that of Wednesday.

Before the dharna, the average attendance of contract workers was between 3600 and 4000, including both at the mother plant and vendor park.

Attendance by engineers also was very thin against an average of 85.

The agitators were also reported to be threatening factory employees staying in rented houses at Baidyabati, Dankuni and Serampore nearby.

Meanwhile, thousands of trucks remained stranded on the Durgapur Expressway running beside the dharna site.