Chennai: The National Investigation Agency (NIA) on Thursday searched five locations in Tamil Nadu's Coimbatore district.
Following intelligence inputs last week about infiltration by six Lashkar men from Pakistan via the Sri Lanka route, security was heightened in the city and the district.
The raids were in connection with persons suspected to have connections with terror organisations.
Five teams of the NIA were carrying out the raids. So far several laptops and pen drives have been seized, an officer said.
The intelligence agencies had warned of planned terror attacks by the infiltrators at places of worship and other vital installations.
The additional personnel put on security duty, including intensified vehicle check and baggage checking, were being scaled down since Monday evening.
Vehicle screening, however, continuing at check posts and defence installations, including the Indian Air Force station in nearby Sulur.
Entire Tamil Nadu was on alert with sensitive installations and places of large congregation coming under police vigil since Friday.
Three people were taken into custody here on Saturday on suspicion of being in touch with a man detained in Kerala for alleged links with terrorists, but released after questioning.
In May this year, an NIA team from Kerala conducted raids at the offices of the SDPI, Popular Front and Thowheed Jamaath in Tamil Nadu.
The raids were in Kumbakonam and Karaikkal regions.
(With inputs from IANS and PTI)