NEW YORK (CBSNewYork) – The George Washington Bridge was open to traffic Friday morning after police investigated a suspicious device late Thursday night.

It was gridlock on and near the GWB from 9:30 p.m. to 11:30 p.m.

Traffic was snarled as Port Authority Police and the NYPD investigated a suspicious object.

A New York man called 911 from his car to report what looked like a pipe bomb in a lane on the eastbound upper span.

A source described the object to CBS2’s Tony Aiello as an 18-inch long metal construction-type pipe. It was about 2.5 inches in diameter, capped on both ends and duct-taped in the middle. The words “INERT TEST” were written on the pipe in magic marker.

“Iconic locations [like] George Washington Bridge will definitely be at the top of everyone’s list,” Matt Whelan, with MSA Security, said.

Whelan, a former NYPD deputy intelligence chief, says given the history of plots targeting the GWB, an incident like this will be investigated on multiple fronts.

“This could be three types of incidents. One, it’s something that fell off a construction vehicle that was used as a site, one is a plant of a hoax device or the third one being an actual dry run by somebody who’s planning to do an attack. You want to come to the final conclusion of which one of those three things that this may be. They’re all concerning in general, but we want to be able to identify why this incident occurred and who may be behind it,” he said.

Whether it’s an innocent piece of construction debris or something more nefarious, Whelan says Port Authority Police will likely use surveillance video and license plate reader data as part of the probe.

“Probably go back to a certain time period before the device was found and try to identify people that were traveling over the bridge at that time,” Whelan said.

Police walked the bridge Thursday night but found nothing else suspicious, and the NYPD bomb squad determined the pipe was not a threat.

The two-hour shutdown was inconvenient for thousands of travelers, but Whelan says it’s as important as ever — if you see something, say something.