Sathuvachary police are investigating the circumstances under which an illegal call centre was functioning from a AC repair shop at THADCO Nagar in Sathuvachary on Thursday.
According to police, Vellore BSNL officials complained that international calls were converted to local calls by an illegal call centre due to which the telecom major was losing revenue.
The complaint resulted in Sathuvachary police visiting the shop from where they seized equipment used to convert international calls to local calls.
Though four suspects were picked up for questioning, police said they were interrogating Abdul Jabbar (27) of Sathuvachary in this connection.
On Thursday, Vellore based IB (Intelligence Bureau) also visited the shop to find out whether the overseas calls had any links to terrorist groups.