Four persons, including a woman, who were held in Surat on Friday on suspicion of being terror suspects wanted by the Mumbai police, were released on Tuesday after it was verified that they were not the same whose sketches were released last week.

A thorough verification of their background was done and the taxi driver was also asked to identify them after they were brought to Mumbai, Maharashtra Anti Terrorism Squad (ATS) chief K P Raghuvanshi said.

"We have come to the conclusion that they are not the ones wanted for doing the reconnaissance of some places in Mumbai and hence released them. Our search for those whose sketches were released on suspicion continues," he added.

"They were with us willingly and not in illegal detention," Raghuvanshi said.

Four people, including a burqa-clad woman, had allegedly hired a taxi on October 22 and 23 and visited five sensitive spots which include Haji Ali Dargah, Mahim Dargah, Mahalakshmi Temple, J J Hospital and Hilton Towers.

The police made sketches of the three men based upon the description of the driver and released them on Friday. The driver had said that the passengers were speaking in Hindi, in a hushed voice and in "Kashmiri" accent.

They were caught while travelling to Delhi on valid tickets after an alert passenger of the Golden Temple Express tipped off police, Raghuvanshi said.

The woman, who was caught, is a bar dancer while one of the men resides in Mumbai itself."The other two are from Lucknow and it was revealed that they are wanted in some petty cases there. We have asked the UP police to take the duo's custody," he added.