In a letter to Maharashtra Chief Minister Prithviraj Chavan, BJP President Nitin Gadkari said following media reports over allegations of involvement of some police officials, it becomes all the more important that the probe be handed over to the CBI so that it is "carried out in an unbiased manner and in a credible way".
He expressed his "deep concern" that investigations into the crime have made no headway even after five days.
Gadkari also urged the Maharashtra Chief Minister to look into the possibility of involvement of underworld dons "from here as well as from abroad" in the murder.
"As I understand, this incident also signals the joining of hands of criminal elements and the terrorist tendencies," he said.
The BJP chief said quick action by the police would create a sense of confidence in the minds of media persons in particular and the people in general.
As Mumbai Police failed to make any headway in cracking the case, there is a move to question former Congressman and oil mafia kingpin Mohammed Ali, currently lodged in a local jail. The hand of oil mafia in killing of 56-year-old Dey last Saturday in suburban Powai is not being ruled out by police.
Chavan, meanwhile, has said that Mumbai Police should not be "undermined" and given a fair chance to investigate the case.