Security was beefed up at Dadar railway station and Dadar Terminus on Tuesday morning after an unidentified man phoned the Railway Protection Force control room warning of a bomb blast.
This is the second threat call made to Dadar station in April.
Personnel from five police stations, the Government Railway Police (GRP), bomb squad and fire brigade spent more than 12 hours searching through Dadar station.
Railway police said the RPF division control at Chhatrapati Shivaji Terminus got a call at 8.10 am threatening to blow up Dadar station at 12 pm on Tuesday.
RPF control then informed police control and railway control, which dispatched platoons to the station.
"We dispatched 22 railway police men and three officers, while the RPF had positioned 12 men on each platform. Mumbai Police, along with its dog squad, and the fire department also sent their men," said Tamai Chekar, deputy commissioner of police (western railway).
"We conducted a detailed search of the station but didn't find anything suspicious — the call was a hoax. We will not discontinue the search until late evening," he said.
S C Padhi, senior divisional security commissioner, RPF, said the call was not a threat but information that the caller passed on.
The caller's exact words were: "Akbar bhai has said Dadar station will witness a bomb blast at 12 pm on Tuesday," said Padhi.
"We've traced the call to a payphone at King's Circle, and are in the process of identifying the caller," added Padhi. On April 13, the Mumbai police control room got a call at around 9.43 am.
The caller, speaking in Hindi, threatened to blow up Dadar railway station between 12 pm and 4 pm. Railway police, with help from the Mumbai Police, combed through the entire station building, and intensified security checks of commuters, but found nothing.
Investigations found the call was made from a payphone at Matunga.