The police custody of Mohd Abdulla Basith, Maaz Hasan Farooq and Syed Omer Farooq Hussaini will start tomorrow.
The three, who are cousins, were intercepted at the Nagpur airport on December 26 when they were trying to board a flight to Srinagar.
The special investigation team of the Hyderabad police had sought 10-day custody to interrogate them. The police said they also wanted to recover certain documents and to take the accused to Nagpur for probe.
The three are at present in judicial custody in Chanchalguda jail here.