(REUTERS) - The Brooklyn Bridge has been shut down in both directions while police investigate a suspicious vehicle, New York City police said on Monday.

An unattended, Manhattan-bound sport utility vehicle was being investigated by the police bomb squad, said New York Police Lieutenant John Grimpel. The historic bridge had been closed since 5.15pm (5.15am Singapore time).

"The bomb squad is responding to deem it safe or unsafe," Mr Grimpel said.

WCBS Radio's traffic correspondent reported the vehicle had no licence plates. With all lanes of the bridge, including pedestrian walkways, closed in both directions at the end of a holiday weekend, traffic was thick and backed up around the bridge, WCBS Radio reported.