WASHINGTON (TNND) — The New York Police Department and the New York City Department of Environmental Protection are investigating groups of people entering sewers at night.

Security cameras recorded at least three separate times that groups of people entered or exited sewer tunnels via maintenance holes on streets in Brooklyn and Queens at night, The Associated Press reported.

A video from early Friday morning in the Williamsburg section of Brooklyn showed a group of about seven people exiting a maintenance hole in the middle of an intersection as cars passed by. Some of them wore headlamps and carried what appeared to be shovels and other tools. One person barely missed getting run over by a vehicle as they pulled themselves out of the hole.

Another video showed a group of about seven people emerging from a maintenance hole around 2 a.m. on a street in Brooklyn’s Gravesend neighborhood. The group headed to a couple of parked cars and took out fresh clothes to change into. The NYPD said that the group entered the sewers about 11 p.m., which means that they could have been underground for three hours.

On May 5, three people were seen wearing waterproof hip waders and other protective gear as they pried open a maintenance hole cover and descended into the sewer on a street in Queens. The last person who entered the sewer pulled the cover shut as approaching cars slowed to a stop.

The Department of Environmental Protection said it inspected the sewers at the two Brooklyn locations and verified the sewer infrastructure wasn’t damaged. The sewer in Queens is still being investigated, according to the agency.

The department’s spokesperson, Rob Wolejsza, said that entering the sewers is both illegal and “extremely dangerous.”

“Sewers can contain numerous hazards, including noxious and potentially deadly gases, unstable surfaces, flooding risks, and confined spaces,” Wolejsza said in a statement. “For these reasons, members of the public should never enter a pipe, drain, catch basin, manhole, or outfall.”

The NYPD said, after conducting a thorough sweep of the areas, that they don’t believe there is any public safety threat. Police added that there have been no reports of injuries or any arrests made, and that the investigation is ongoing.

Sources told the New York Post that the NYPD and Department of Environmental Protection investigations found that the incidents appear to be people scavenging for anything of value. The sources added that urban scavenging for lost valuables like coins, wallets, scrap metal, or jewelry is a more common practice in other countries.

The NYPD said that it wasn’t immediately clear if the two Brooklyn incidents were connected.