A New York City official confirmed Wednesday that police and other municipal employees are looking into reports – including ones based on videos – of people entering sewers at night and emerging hours later.

The incidents have been recorded on security cameras over the past few weeks.

The footage captures at least three events at night in which people have entered and exited sewers via maintenance holes in Brooklyn and Queens. It remains unclear if the same group is behind the incidents.

“There were no injuries reported. There are no arrests, and the investigation remains ongoing,” a police spokesperson told NBC News regarding two Brooklyn incidents.

The city Department of Environmental Protection, which manages the system, said it inspected both Brooklyn incident locations and found no damage to the sewer.

Some of the people wore headlamps, waders and carried tools as they headed into the manholes. In one of the instances, according to the Associated Press, about seven people emerged from a maintenance hole around 2 a.m. in Brooklyn’s Gravesend neighborhood. They walked to nearby parked cars and changed into fresh clothes. Police said the group entered the sewers around 11 p.m.

The wire service also reports a May 5 indecent in Queens.

If caught, these people could face burglary charges, not to mention, the sewer system is filled with overpowering fumes and tunnels that can fill with heavy rain.

The New York City sewer system has been attracting visitors and, oftentimes, inhabitants, for years. A number of articles in The New York Times dating back to the late 1800s reveal information about gems, unopened mail and missing pets. The sewer has been a getaway for escaped convicts and bodies have been found there.

The 1984 cult-classic horror film C.H.U.D. tells the story of mutant creatures living in the sewer system below New York City. In urban exploration lore, the term “mole people,” refers to individuals who dwell underground.