Durgapur, Aug. 6: At least a dozen witnesses have told police that they saw Trinamul trade union leader Kedar Pal beat up Eastern Coalfields Ltd contractor Ashim Mukherjee and bang his head repeatedly against a wall last week.

Mukherjee died of haematoma, a swelling of clotted blood, at the back of the head, according to the post-mortem report. An INTTUC leader had spoken of a heart ailment as the probable cause of death.

“All the witnesses we interrogated today said the same thing. Contractor Ashim Mukherjee was beaten up by Kedar Pal. Our investigation is in full swing,” said Sunil Yadav, the additional deputy commissioner of police (east).

According to police sources, the witnesses include Kartik Dhibar, Mukherjee’s employee who was with him when the contractor was attacked allegedly by Pal.

“We have learnt that Pal kicked and punched Mukherjee and then banged his head against a wall and an iron wheel. The contractor fell unconscious and started frothing at the mouth. Before the attack, Pal had taunted Mukherjee over a helmet,” another police officer said.

Pal, who is in police custody, has denied assaulting Mukherjee. He claimed Mukherjee fell to the ground clutching his chest.

Trinamul Pandaveswar block president Narendranath Chakraborty, who looks after INTTUC-affiliated unions in the area, had said Mukherjee had “cardiac ailments”.