Sections of the Mumbai commuter rail network were briefly shut down Saturday afternoon after an anonymous caller phoned in a bomb threat, officials said. The threat was later revealed to be a hoax.

The caller said the bomb had been placed at the station in the Mumbai neighborhood of Vile Parle, said Pranai Prabhakar, spokesman for the Western Railway. The station was evacuated, and some train services were stopped while police sniffer dogs checked out the station. No bomb was found, he said.

CountryWatch: India

Police searching for clues in Mumbai's deadly commuter train bombings swept through several neighborhoods Saturday, rounding up more than 300 people for questioning, officials said.

Only 11 of those brought in were detained — all for petty crimes unrelated to the serial bombings — said senior police inspector Joseph Gaikwad.

Police have launched such sweeps repeatedly since the blasts. Saturday's house-to-house searches were conducted mainly in the slums of the city's Mahim neighborhood, an area popular with illegal immigrants from Bangladesh. This city of 16 million attracts people from across India and South Asia searching for jobs.

"This was a routine combing exercise. We have questioned and released all but 11 of the 307 who were brought in from Mahim," Gaikwad said.

The 11 are not thought to have been involved in Tuesday's bombings that killed 200 people, but police believe that they may have information about the bombers.

Police began random frisking of commuters on Mumbai's rail network and closed-circuit television cameras were installed at six busy train stations on Saturday.

"Soon all stations will be monitored by closed circuit television," said a railway spokesman, Pranay Talwalkar. "Whenever they find suspicious looking people or commuters carrying unusual packages, police have the authority to search those individuals."

The police sweeps and increased security came a day after Prime Minister Manmohan Singh said the bombers who targeted Mumbai's rail system had support from inside Pakistan, warning that the nuclear-armed rivals' peace process could be derailed unless Islamabad reins in terrorists.

Singh's unusually blunt comments appeared to signal an abrupt shift in relations between India and Pakistan, whose ties had warmed over the past two years.

Initial fallout came quickly, with talks between the foreign secretaries of India and Pakistan planned for July 20 canceled, Indian media reported Saturday.

"Cooperation is a two-way street," Indian Foreign Secretary Shyam Saran told reporters Friday, but he declined to comment on the status of the talks.

On Saturday, police said a former employee of an international bank, arrested last month for allegedly siphoning off nearly half a million dollars from customer accounts, has links with Pakistan-based militants.

Police have "conclusive evidence" that Nadeem Kashmiri had contacts with the Pakistan-based Lashkar e-Tayyaba militant group, said Inspector General of Police Sushant Mahapatra. This was revealed during lie detector tests.

But it is not known if Kashmiri had anything to do with the Bombay blasts.

Investigators were casting a wide net for the Mumbai bombers, focusing on Lashkar-e-Tayyaba, along with smaller homegrown groups.

Mumbai Police Commissioner A.N. Roy said a man known only as Rahil was the third person sought in connection with the blasts. The other two suspects have been identified as Sayyad Zabiuddin and Zulfeqar Fayyaz.

Roy said those two suspects have been on the run since May.

Pakistan has denied India's accusations that it had a hand in the blasts. The spokeswoman of its foreign ministry, Tasnim Aslam, called Prime Minister Singh's allegations "unsubstantiated."

Singh had told reporters on Friday that investigators are certain that terror cells operating in India "are instigated, inspired and supported by elements across the border, without which they cannot act with such devastating effect."

Singh noted that Pakistan had assured India two years ago that its territory "would not be used to promote, encourage, aid and abet terrorism.

"That assurance has to be fulfilled before the peace process and other processes progress," he said.

After coming to the brink of war in 2002, India and Pakistan began a peace process that has brought them closer, yet concrete agreement on the most pressing issue — the Himalayan region of Kashmir — has been minimal.