Capitol Police on Thursday morning discovered a small metal cylinder on Pennsylvania Avenue NW near the reflecting pool in front of the U.S. Capitol.

Streets were shut down and a robot was called in to investigate. But the suspicious device was eventually found to be nothing more than a piece of equipment used to inspect sewer pipes, according to NBC News correspondent Pete Williams.

An officer spotted the object at about 7 a.m. Thursday, and law enforcement officials said they were investigating it as a suspicious device.

Investigators put the device into an X-ray machine, but Capitol police said "it was too dense to see what's inside."

A team placed the cylinder inside a bomb squad vehicle, and it was to be transported to Quantico, Va.

Surrounding roadways were shut down for the investigation. The affected roads: First Street NW from Garfield Cir. to Constitution Ave. and Pennsylvania Ave SE from First Street to 3rd street SE.

D.C. Fire and EMS tweeted that some roads were still closed before 10 a.m.