NY subway odour 'not terrorism'

New York is on high security alert

An "unknown substance" which led to the hospitalisation of five New York subway workers is not terrorism-related, officials say.

"No subway line has been shut down or evacuated," a police official said.

Emergency services were checking Manhattan's southbound "F" line for the substance, fire department spokesman Paul Iannizzotto said.

The odour was detected in a tunnel amid heightened security on the eve of the American Thanksgiving holiday.

New York has been on the highest possible security alert since the 11 September 2001 attacks.

Last week, the US authorities warned that al-Qaeda continued to plot attacks on American interests abroad.