The office of IT major Wipro at the Salt Lake Electronic Complex in Kolkata, was evacuated after an anonymous caller claimed a bomb had been planted there, but police have found nothing after five hours of search.
IGP (Law and Order) Raj Kanojia said the phone call was received by the reception at 3:45 pm and the caller spoke in Bengali.
He said the explosive is timed to go off late in the night, a Wipro statement said.
Police, RAF personnel and bomb squad aided by sniffer dogs have launched a massive search, examining packages, parcels and equipment. But nothing has been found so far, the IGP said.
The South 24 Parganas district police led by Superintendent of Police Praveen Kumar cordoned off the premises. There was some tension in adjoining residential areas.
"A complete search was conducted by the police and business continuity plans are in place and disruption if any is expected to be minimal," Wipro said, adding that evacuation plans were in place.