Patil said that the perpetrators were smart enough not to have left any clue for the police to track them down.
"There are some criminals who are very smart. They are not leaving any clues. That is why investigation is becoming a little tough," he said responding to reporters's queries.
Patil, however, reposed faith in the abilities of Mumbai police and said the investigation in Dey's murder was progressing in the right direction.
"We have full faith in the ability of Mumbai police. These people (police) are on the right track and will surely catch the accused. They should be given sufficient time. We don't want to do anything that will discract or divert their focus," he said.
Dey, Editor (special investigations) with city tabloid Mid Day, was gunned down by four assailants last Saturday.
Though the police had apprehended three persons believed to be members of the gang of Choota Shakeel, the right hand man of fugutive ganglord Dawood Ibrahim, they were let off apparently after police found no evidence of their complicity in the crime.