Hundreds of firefighters, police and medical personnel descended on lower Manhattan on Sunday near the site of the September 11 attacks for an emergency response drill simulating an explosion on a commuter train in a tunnel between New York and New Jersey.

Large sections of the financial district were closed to vehicles and pedestrians as emergency vehicles raced to the area with lights flashing and sirens blaring in the largest such practice event since the 2001 attacks.

Authorities issued warnings of the event, trying to avoid panic like one caused by an unannounced flyover by a U.S. presidential plane in New York Harbor just weeks ago.

The exercise, involving more than 800 emergency services personnel, simulated the aftermath of a pair of bombs exploding on a commuter train with hundreds of injured passengers, all complicated by a malfunctioning communications system.

It began around 8 a.m. EDT, with train service at the transit hub, still surrounded by construction sites for skyscrapers and a memorial for victims of the September 11 attacks, due to resume by noon.

The World Trade Center site has been attacked twice, first by a truck bomb in 1993 and then in the September 11 attacks that destroyed the Twin Towers. Madrid, London and Mumbai have since been hit by transit system attacks.

On April 27 a plane sometimes used by President Barack Obama, trailed by a fighter jet, flew low over the Statue of Liberty near the World Trade Center site, creating panic in the financial district still reeling from memories of September 11.

The flight, not publicly announced, was staged for a photo shoot. A White House aide later resigned over the incident.

(Writing by Chris Michaud; Editing by Eric Walsh)

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