Police in New York have ruled out a terrorist link to an explosion in midtown Manhattan last night.
The blast in a steam pipeline sent debris flying into the air and caused panic and chaos during the evening rush hour at around 6pm local time.
It led to the evacuation of thousands of people from the major subway and commuter rail hub at Grand Central Station and from nearby offices.
Several blocks of Lexington Avenue near the Chrysler building remained closed off into the evening.
Mayor Michael Bloomberg told reporters that one person died from a heart attack following the incident and 20 others were injured.
Four firefighters were treated for minor injuries at the scene.
It is understood a 60cm steam pipe, installed in 1924 and used in the heating and cooling systems of office buildings in the area, burst due to to rain water from a morning deluge seeping into the pipe.
A spokesperson for electrical supplier Con Edison said the company was testing the air for asbestos as a precaution.
A similar steam pipe explosion in 1989 killed three people and caused a health alert due to asbestos being released into the air.
