Purulia police on Sunday sought the help of the state forensic department in its probe on the murder of Congress councillor Tapan Kandu of Jhalda municipality after it failed to crack the case even after a week of the incident.

“We sought help from forensic experts to get some clues from the spot... We are trying to arrest the people directly involved in the murder. We are interrogating the nephew of the victim councillor in our custody,” said S. Selvamurugan, the Purulia police chief.

Sources said a team from state forensic science laboratory visited Purulia on Sunday and collected evidence like bullet shells and injury reports of Kandu.

Purulia police on Sunday shunted five police personnel, including a lady sub-inspector of Jhalda police station to Belguma police line in district headquarters on charges of negligence in duty. The five were part of a team to patrol the roads of Jhalda town on March 13 evening when the councillor was shot dead. The councillor’s family had accused those police personnel for not responding even after repeated requests, said a senior officer.

Sources said the police are under tremendous pressure as they failed to crack the case. Dipak, the nephew of the councillor who had contested against him, was arrested. “We arrested him as he was the accused in the complaint and primary evidence went against him. But he could not give us a proper lead during interrogation. We are continuing the interrogation,” said a police officer.

Kandu’s family members are urging for a CBI probe.

Kandu’s family had accused the inspector in charge of Jhalda police station Sanjib Ghosh of pressurising Kandu and his wife Purnima to join Trinamul. Ghosh has not been removed or shunted as yet.

In Panihati in North 24 Parganas, where Trinamul councillor Anupam Dutta was shot dead the same day as Kandu, a police team headed by deputy police commissioner (north) Shrihari Pandey visited the spot.“Till now, three persons have been arrested, but the mastermind is elusive,” said a source. Police visited the pet shop from where Dutta had bought medicines for his puppy and questioned traders.

So far, the police have arrested three persons including shooter Amit Pandit. A police team of Barrackpore interrogated Pandit and Jiarul Islam, who was earlier allegedly given the contract to kill the councillor, together.