It's common for passengers to stand while riding inside city buses, but on Tuesday afternoon a passenger was spotted standing on the roof of a Maple Grove Transit bus as it rolled along a freeway in north Minneapolis.

Motorists with their cellphone cameras caught the action of a woman waving her arms and stumbling atop the articulated bus and posted photos on social media. Minnesota Department of Transportation cameras also showed the passenger lying down on top of the bus at about 4 p.m. as it traveled on eastbound Interstate 94 near the Dowling Avenue exit.

"Yesterday was a wild one," said Mike Opatz, a spokesman for the suburban transit agency. "It's not your run-of-the-mill incident. We hope we never see it again."

The express route 781 had dropped off passengers at the Maple Grove Transit Station and was thought to be empty as it was returning to downtown Minneapolis to begin another run. The woman, Opatz believed, had taken the bus to Maple Grove, but then hid behind a seat. During the trip to downtown, she opened a hatch and climbed onto the roof.

"You have to be nimble to do that," Opatz said, noting the opening is quite small.

Drivers on the freeway called 911 and Metro Transit police and the State Patrol responded. Richard Weaver was behind the bus and said he was "shocked" at what he was seeing.

"I thought maybe I wasn't seeing it right," he said. "Then she nearly fell off the bus."

Weaver got along side the bus and motioned and waved to the bus driver to pull over. "Somebody is on your roof," he said.

The bus driver about that time also knew something was amiss and pulled over, Opatz said.

"The operator alertly and carefully pulled the bus over onto the shoulder of the interstate and no injuries were reported," said Drew Kerr, a Metro Transit spokesman. Metro Transit provides drivers for Maple Grove.

No one was hurt in the incident.

The move was extremely unsafe, and no one else should attempt it, MnDOT said in a statement that accompanied the video.

"We are glad it didn't turn out worse," Opatz said. "It was very strange."

Authorities continue to investigate the incident.