State police, while sharing information with their Maharashtra counterparts "to avoid investigations being affected by rumours generated from different quarters," have rounded up SIMI activists in Bhopal, Khandwa, Indore, Ujjain and Burhanpur districts, they said.

"No formal arrest was made as most of them were released after interrogation," a source said, adding that the probe would continue as efforts are being made to trace known office-bearers of the banned group, most of whom have gone underground.

Conclusive evidence to link state-based SIMI activists with the Mumbai blasts is yet to be found, though a prankster was arrested on Wednesday for sending an e-mail to a newspaper office about the attacks, they said.

In the wake of Maharashtra's Anti-Terrorism Squad tracing another e-mail reportedly from Lashkar-e-Qahhar sent to a TV channel in the state, another person was held after raids, the sources said.

Details about him are being collected and he is being interrogated, they said. In a bid to ensure coordinated efforts, a senior officer of the rank of additional director general of police rushed to Mumbai to maintain contacts with the ATS that is probing the July 11 blasts on commuter trains, which killed 200 people, they said.