The CBI probe into the Mecca Masjid bomb blast, which killed 11 people, commenced on Monday, with the arrival in Hyderabad of a team from the agency.
The CBI tean held discussions with the city police top brass after registering a case.
The team led by SP Jakkhad arrived from Delhi and began the process of inquiry, city Police Commissioner Balwinder Singh told PTI on Monday night.
The state government had ordered the CBI probe into the bomb blast in the mosque on May 18.
Meanwhile, an inquiry by special executive magistrate Ramesh Reddy began into the police firing after the bomb explosion in the mosque in which six persons were killed.
Earlier, the CBI registered a case to start probing the Mecca Masjid bomb blast.
The CBI sources said a case had been registered against unidentified people under the Indian Penal Code and Explosives Act and approached Andhra Pradesh government for the evidence gathered so far.
A six-member team has been constituted to probe the blast that had rocked the historic mosque during Friday prayers on May 18.
The decision to handover the probe to CBI was taken by Chief Minister Y S Rajasekhara Reddy on May 24.
The state government decided to go for a CBI probe following representations by some Muslim organisations that they could be targeted if the probe is conducted by the state police.