An Interior Ministry official said the chain of events that led to the May 18 blasts began with Lashkar-e-Toiba operative Sheik Abdul Nayeem, alias Sameer, smuggling 15 kilograms of RDX from Bangladesh. Before he was caught on the India-Bangladesh border in April, he smuggled in two Bangladeshi and two Pakistani mercenaries, a spokesman for Hyderabad police said.
The RDX was then sent to Hyderabad, along with other explosives, he said.
"About eight to 10 bombs were assembled at the residence of one Imran Khan, a blast accused, in the city. We have his video-graphed confession," the police said.
State police said two bombs were used in the Mecca Masjid blasts and two in blasts that targeted a Sufi shrine in the northern city of Ajmer.
"There are four or five bombs still hidden somewhere along with the unspent RDX," a senior police officer said.
Three men planted the bombs in the Mecca Masjid, Indian officials said. One of them, a native of Hyderabad, was arrested; two others -- identified as Bangladeshis -- crossed the border after the blast, the spokesman said.