Police in bio-hazard suits partially cordoned off one of New York's main transport hubs Friday, fraying public nerves already on edge following the threat of a terrorist attack on the city's subway system.
Police officials said they were investigating a suspicious substance that had been reported in a soft-drink can near an Amtrak inter-city line at Penn Station in midtown Manhattan.
Despite the heavy security response, which included National Guard troops and sniffer dogs, an Amtrak spokesman stressed that the risk was minimal.
"There was no danger to anyone at any time," the spokesman told reporters. "The train service was not affected at all, nor were any parts of the station evacuated."
The decision to cordon off the area was made at the request of the police, he said, adding that they were "testing and investigating the substance."
The scare came a day after city officials warned of the most specific threat to date of an attack on what is one of the world's largest subway systems.
"This is the first time that we have had a threat with this level of specificity," Mayor Michael Bloomberg told a press briefing Thursday. "It was more specific as to target, it was more specific as to timing."
There was a heavy police presence in subway stations Friday morning, with random searches of bags and baby strollers, which had been cited as a possible method of concealing an explosive device.