George Washington Bridge
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George Washington Bridge
A "hoax device" that looked like a pipe bomb led police to completely shut down the George Washington Bridge on Thursday night, a law enforcement source said.

The fake device — a piece of pipe capped on both ends — was planted in the middle of the upper level near the bridge's New Jersey tower, said the source.

A passing motorist noticed the pipe and called the cops.

The bridge's upper level was shut around 9:37 p.m., the Port Authority said. The lower level was reported shut at 10:21 p.m.

Frustrated motorists took to Twitter to ask when the bridge would reopen. The incident also caught Mayor de Blasio's attention.

"NYPD is responding with its partners to a suspicious device," de Blasio said on Twitter. "Expect detours and delays around the GWB approaches. Use alternate routes."

Police determined that the pipe was inert, the law enforcement source said.

The Port Authority said at 10:51 p.m. that the bridge's lower level was reopened, and at 11:11 that the upper level was reopened.

The incident remained under investigation late Thursday night.