Mumbai: The CBI is likely to take custody of Sharad Kalaskar, who has turned a suspect in the murder of rationalist Narendra Dabholkar since his arrest by the Maharashtra anti-terrorism squad in a terror plot case a fortnight ago.

The CBI, probing Dabholkar's assassination which happened five years ago to this day, had on Saturday arrested Sachin Andure, who has allegedly confessed to shooting the author near Pune's Omkareshwar bridge.

Andure was arrested reportedly after Kalaskar provided leads during questioning and confessed he was himself one of the motorbike-borne killers.

Sources in the anti-terrorism squad (ATS) said Andure and Kalaskar had done a recce of the area a week before the murder.

"They tracked the route the victim took. The night before the murder they came to Pune from Aurangabad," a senior officer said.

"They were provided with logistical support, such as motorbikes, to carry out the murder and escape through a route that was not covered by closed-circuit television cameras."

He said the killers are believed to have dumped the motorbikes on Pune's outskirts and returned to Aurangabad.

It was Karnataka police's special investigation team (SIT), which is probing the murder of journalist Gauri Lankesh in Bangalore last September, which provided the initial clues about the involvement of Andure and Kalaskar.

A CBI source said that another person whom the Karnataka SIT had arrested in connection with Gauri's murder too had played a role in Dabholkar's assassination.

"We suspect the man was a conspirator along with Virendra Tawde (a doctor named as the main conspirator in the chargesheet and out on bail). We are looking at his statements and will seek his custody at the appropriate time," the officer said.

The CBI and the Maharashtra ATS are working in close coordination with the Karnataka SIT as there are overlapping features in the killings of Dabholkar, his fellow rationalists Govind Pansare and M.M. Kalburgi, and Gauri. All four murders were committed in Maharashtra and Karnataka between August 2013 and September 2017.

"We have call records and emails detailing the exchanges between some people arrested by the Karnataka SIT and some we have picked up. Several of those arrested by the Karnataka team are from Maharashtra," an ATS officer said.

On the fifth anniversary of Dabholkar's murder, his relatives and the Maharashtra Andhshraddha Nirmoolan Samiti, a group that campaigns against superstition, organised a march from the spot where he was shot.