Four persons, including a woman whose identities are suspected to be similar to the sketches of people who had carried out reconnaissance of five sensitive spots in Mumbai have been detained in Surat, the police said in Mumbai on Saturday.

"The Railway Protection Force in Surat has detained the four persons from a train on Friday night following the release of the sketches yesterday. We are ascertaining if they are the same people," Anti-Terrorism Squad K P Raghuvanshi told PTI in Mumbai.

Raghuvanshi said that some of the detained are said to be from Lucknow, but refused to give further information on them saying the process of ascertaining their identity is underway.

Police released sketches of three persons on Friday who apparently carried out reconnaissance of sensitive spots in the city like Mahim dargah, Haji Ali dargah and Mahalaxmi temple last week.

Along with a burqa-clad woman, the trio had used a taxi for travelling around Mumbai for the 'recce' on October 22 and 23. The sketches were made as per the description given by the taxi driver, police said.

The suspects allegedly asked the taxi driver to keep two bags containing 'unknown material' with him while leaving the cab near the Siddhivinayak temple on October 23, following which the driver got suspicious and had a heated argument with them.