No one was arrested Thursday afternoon after authorities determined that a substance that prompted an alert downtown was not “red mercury.”

“The scene was cleared soon after,” Atlanta police spokesman Donald Hannah said Friday. “There were no arrests made.”

Officials investigated after reports that a man claiming to have “red mercury” from Africa walked into the regional office of the U.S. Nuclear Regulatory Commission, police said.

Red mercury is reportedly a substance used to create nuclear bombs, but its existence has not been documented, The Atlanta Journal-Constitution reported.

U.S. Homeland Security agents also responded, police said, and a hazmat team, bomb squad and fire trucks were seen near the scene. Parts of Peachtree Street, Peachtree Center Avenue and Courtland Street were closed during the incident.

Police did not say what substance actually was found.

In other news:

Police are investigating why employees didn't follow protocol when a 6-year-old boy was left alone on a bus for hours.