A massive search operation has been launched to find the missing RDX allegedly smuggled into Hyderabad even as 15 people, including key terror suspect Mohammed Shahed alias Bilal, have been booked for conspiring to carry out bomb attacks.

Police sources said a small portion of the RDX was used in Mecca Masjid blast on May 18.

Sameer alias Abdul Nayeem, one of the four arrested in connection with that blast, reportedly disclosed the information about the RDX being smuggled in during a narcoanalysis test, sources said.

The city police had on Saturday slapped cases against Bilal and 14 others under the Explosives Act and for conspiring against the state. This includes the four persons who were arrested and 11 who are untraceable.

"We have found a conspiracy to bring RDX to India and we have arrested some persons in that connection. One Samir was arrested by Maharashtra police and we got him on police remand and during interrogation he has confessed to have brought RDX," city police commissioner Balvinder Singh said.

"Number of couriers have helped him. All these people are being booked in that conspiracy case but RDX was brought from Bangladesh," he added.

The police registered cases on the basis of revelation by Sameer that 10 kg of RDX was smuggled to the city on the direction of Bilal from Bangladesh in February, sources said.

Bilal, a resident of Moosarambagh area in the city, is believed to be working as the self-styled South India commander of Harkat-ul-Jihad-Islami, intelligence sources said.

The most wanted terrorist is said to have masterminded the twin blasts on August 25 and is being also framed for his involvement in the Mecca Masjid blast in the old city area.