Police and bomb squad agents are investigating a suspicious vehicle near Union Square in New York City on Thursday.

A pedestrian reportedly saw two gas canisters inside the parked car and called police.

Streets and buildings nearby have been evacuated as a precaution, and bomb squad agents with a robot and emergency personnel are still working at the scene. The bomb squad headed back to the car after withdrawing briefing, reports said.

There has been a major jump in 911 calls on suspicious packages since a failed car bomb plot on Times Square two weeks ago. Thursday's was the fourth bomb scare since then.

On May 1, a crude car bomb made from gasoline, propane, firecrackers and alarm clocks was discovered in a smoking van on Times Square, and thousands of tourists and theatergoers were evacuated from the so-called "crossroad of the world."

On May 3, a naturalized U.S. citizen from Pakistan, Faisal Shahzad, was arrested at John F. Kennedy International Airport.

Investigation has been ongoing, with three others arrested Thursday in connection with the botched bomb plot.