PORTLAND, Ore. (KOIN) — Portland’s Bureau of Environmental Services will make changes to part of the city’s sewer system after surveillance video captured people emerging from a manhole on 2 different nights.

The surveillance videos from Chown Hardware caught the people popping out from underneath a manhole on NW Front Street outside their warehouse near the railyard on June 2 and June 13.

One video shows 3 people, the other shows 5 people. One of the people even waves at passing cars.

Watch: Surveillance video from Chown Hardware, June 2, 2019

David Chown, the co-owner of Chown Hardware, said the cameras were installed just a couple months ago but they think this has happened before.

“We’re pretty sure that it’s happened before because our neighbors in the same building that we’re in said that they’ve seen the manhole cover move and their drivers have said they’ve seen people coming out,” Chown told KOIN 6 News. “So apparently it’s not as rare as we thought it was.”

Manager Kris Lake spotted a shoe near the manhole cover and wondered how it got there.

“I checked the footage and I definitely did not expect a manhole cover to pop up,” Lake said. “I wanted to at least report it because maybe there’s something suspicious going on. Maybe there’s something illegal going on, maybe they robbed somebody and jumped into the sewers.”

The manhole outside Chown Hardware goes down more than 20 feet and leads to a 60-inch pipe. This pipe carries mostly storm water but can also hold overflow sewage from heavy rain.

City officials think they now know where these people entered the sewer.

BES officials began looking for damage to the sewer system after learning of the incidents. They said the entrance to this pipe isn’t visible to the public. It has some damage they’re going to repair.

They also plan to upgrade the pipe’s entrance next summer and said they now plan to add some extra security barriers.

It’s illegal to move manholes or enter the sewer system. Anyone caught doing it faces thousands of dollars in fines and be on the hook for the cost of repairs.

Beyond that, it’s dangerous, even deadly. Sewer pipes have low oxygen levels, harmful bacteria and can flood at any time.

If you see something like this, BES said the best thing to do is call their 24 hour Sewer Repair Emergencies Hotline to report it — 503.823.1700.

“We’ve been in business 140 years and I never would’ve dreamed, we’ve never seen anything like that in all the time we’ve been in business,” Chown told KOIN 6 News. “It’s very crazy.”

“I didn’t even know it was a thing,” said manager Kris Lake. “You go about your day and you don’t think about people under the ground.”

“I can think of a lot more fun things to do than crawl around in a sewer,” Chown said.

Watch: Surveillance video from Chown Hardware, June 13, 2019