NEW YORK, Jan 8: A powerful, mysterious smell of natural gas wafted over much of Manhattan and parts of New Jersey on Monday, forcing building evacuations and a temporary suspension of commuter train service before dissipating.

Seven people were hospitalised in New Jersey, just across the Hudson River from New York, even though Mayor Michael Bloomberg said the odour was not dangerous and no unusual gas leaks had been found.

“It may just be an unpleasant smell, but at this point we do not know any more than that. The one thing we are confident about is, it is not dangerous,” Mr Bloomberg told a news conference.

“The city's air sensors do not report any elevated level of natural gas,” he said.

The gas-like smell permeated lower Manhattan and was detected as far north as Central Park, across the width of the island, and in New Jersey.

The wide extent of the odour provoked jitters in a city that is constantly reminded of the

Sept. 11 attacks. Police and fire sirens sounded throughout much of the city.

A U.S. Department of Homeland Security spokesman said “there is no indication at this time of a terrorism connection.”

Seven people sought treatment in emergency rooms in New Jersey complaining of symptoms relating to the odour, said Nathan Rudy, a spokesman for the New Jersey Department of Health and Senior Services.

Four schools in Manhattan were briefly evacuated, and the smell chased people out of landmarks such as the Rockefeller Center and Macy's department store.

“It was really, really bad then, so bad it gave me a headache,” said Kate Browne, who lives in the West Village neighbourhood and said she could smell the gas when she took her daughter to school.

“The emergency services turned up at my daughter's school looking for the leak then,” she said.

Part of the New York-New Jersey PATH train system, which carries 225,000 passengers a day, was shut down temporarily as a precaution but normal service quickly resumed.—Reuters