A special investigation team, SIT, of Mumbai police, probing the murder of senior journalist Jyotirmoy Dey, on Sunday visited his mother’s residence at Amrut Nagar in Ghatkopar as well as his house in Powai. Joint Commissioner of Police (Crime) Himanshu Roy said preliminary investigations by the crime branch have revealed that the assailants may have been hired from outside the city and Dey's recent articles on oil mafia might be the immediate trigger behind the murder.