A district court in Amravati on Sunday sent the key accused and the mastermind in the murder of chemist Umesh Kolhe to police custody till July 7.
The accused, identified as Sheikh Irfan Shaikh Rahim alias Irfan Khan, was arrested by Amravati police in Nagpur on Saturday.
He is the seventh accused to be arrested in the case.
The number of arrests may increase, said a police official on Sunday.
"He (mastermind) was arrested last night. He's being interrogated. They have a helpline group-Rehbar group. Several people connected to them. 7 accused have been arrested so far. The number of arrests may rise after the arrest of the main accused," said Nilima Araj, Police Inspector when asked about the mastermind of Amravati murder.
Police had earlier said that on the face of it, the killing of Kolhe (54) was linked to certain posts that he had shared in WhatsApp groups, supporting Nupur Sharma who has been suspended by the BJP for making controversial comments about Prophet Mohammad.
A team of the National Investigation Agency (NIA) interrogated Khan on Sunday morning at the city Kotwali police station, before he was taken to the Amravati district and sessions court amid tight security.
A Union Home Ministry spokesperson had earlier tweeted that the investigation has been handed over to the central probe agency.
Meanwhile, Maharashtra Deputy Chief Minister Devendra Fadnavis on Sunday said the murder in Amravati was a "very serious incident". He added that the National Investigation Agency (NIA) was trying to find out if there were any international connections to the incident.
"Amravati incident very serious, killing is barbaric. Accused, mastermind nabbed. NIA investigating it, finding if there is some international connection. This was initially portrayed as theft, that too will be investigated," said Fadnavis.
(With PTI and ANI inputs)