Sources said that the trio including two Pakistanis and India's most wanted Yasin Bhatkal alias Shahrukh of Indian Mujahideen had rented the apartment six months back.
It is also learnt that, during their stay in Mumbai, they travelled to the national capital to plant the bomb in the Delhi High Court, which killed 11 people and left over 70 injured in Sept last year.
Media reports claimed that the apartment was rented out some time in Apr last year prior to the Mumbai serial blasts that left 26 dead and over 100 injured.
Meanwhile, the door of the apartment is now locked and it is believed that trio fled the country earlier this month. The Maharashtra Anti Terrorist Squad (ATS) has detained the owner of the apartment, a woman for questioning.