Mumbai Crime Branch has detained at least four persons in connection with the ongoing probe of the July 11 serial blasts in commuter trains, sources said on Saturday.

The four suspects, including two highly qualified professionals, were detained from a locality in central Mumbai two days ago, sources said, adding that no decision had yet been taken yet with regard to their arrest in the blasts case.

The Crime Branch, besides lending its men who have probed the 2003-2004 blasts to the Anti-Terrorist Squad, has also initiated an independent probe into the serial train blasts, the sources said, adding that the two suspects were detained from Parel in central Mumbai earlier this week, followed by detention of two more persons two days ago.

"We have some information about their likely involvement in the blasts, and we will doubly confirm it before we place them under arrest," a senior Crime Branch official told PTI in Mumbai.