"Vinod Asrani alias Vinod Chembur, a bookie who was suspected to have helped the shooters identify Dey, was picked up for questioning and subsequently arrested," said a Crime Branch official.
"We have information that he (Asrani) held a meeting with shooters days before the murder and also handed over money to the killers," the official alleged.
Asrani was produced before a local court, which remanded him to police custody till July seven, the official said.
Joint Commissioner of Police (Crime) Himanshu Roy and Additional Commissioner of Police (Crime) Deven Bharti were unavailable for comment on the development. Neither of them replied to text messages.
Last Sunday night, police had arrested gunman Rohee Thangappan Joseph alias Satish Kalya (34) and his associates Abhijeet Shinde (28), Arun Dake (27), Sachin Gaikwad (27), Anil Waghmode (35), Nilesh Shendge (34) and Mangesh Agawane (25) in connection with Dey's murder.
J Dey (56), working with the city-based English tabloid Mid Day, was shot dead by four motorcycle-borne assailants in suburban Powai on June 11.
Police claimed the journalist was eliminated at the behest of Rajan, who paid Rs five lakh to the accused. However, they said the motive behind the killing was not yet clear.