Friday afternoon in Federal Way, Wash., a city to the south of Seattle, utility workers came across a manhole that refused to stay closed.

Meter readers with Lakehaven Utility District first noticed the sewer cover left ajar. They pushed it shut; to fall down an open manhole, after all, could mean injury or worse. It proved to be a stubborn grate. Later in the day — twice — workers found the manhole open again. The third time, the meter readers had enough, summoning the Lakehaven sewer crew, who decided to investigate how a 80-pound metal slab could behave like a screen door with a busted latch.

What the crew found was even stranger. At the bottom of the 14-foot descent was a cache of kids’ items, miscellany that belonged in a treehouse or rec room: a pair of binoculars, snacks and toys, including a pistol for shooting foam darts. They discovered clothes, too, as well as a makeshift bed made out of plywood.

“This should not happen at all,” as Ken Miller, a product engineering manager with Lakehaven Utility District, told KIRO 7 News. “This is where all our waste goes from our houses and our businesses.”

And, finally, the crew noticed the two boys watching.

They appeared to be about 12 or 13. When approached, one said he had been living within the manhole. Miller was shocked. “I’ve been doing this kind of work for over 30 years, and I’ve never, never come across it before,” he said. “No one should be down there … this could have been life and death.”

He warned the children that the sewers were dangerous, according to Fox 8. Crews like Lakehaven’s wear protective gear when entering the sewers. Methane gas can build up in the system, a byproduct of decomposing waste. Though not harmful at low concentrations, if the gas displaces enough oxygen it can be suffocating. Would-be sewer spelunkers may also encounter rodents and other animals that carry disease. If a car were to park above the sewer cover, the children could be trapped below.

Such hazards do not mean the systems are always uninhabited. As Jennifer Toth famously wrote in her 1995 book, “The Mole People,” within the New York City underground live some 5,000 homeless who have found shelter in the sewer systems and old subway lines. Disputes about the details of Toth’s account aside (one critic said that her adventurous tone was an attempt to spice up “sad visits to dirty holes in the ground”), subsequent reporters and photojournalists have documented homeless living in urban tunnels, not only in New York but cities like Las Vegas as well.

As for the children in Federal Way, people living in the neighborhood said the kids had been occasionally spotted above ground. Of the 2.5 million homeless children estimated across the United States in the 2012 to 2013 school year, more than 60,000 lived in Washington state. That young homeless population puts the state at the 40th worst out of 50 states, according to the National Coalition for the Homeless.

Though the manhole had been seen uncovered at various times throughout the past month, it was unclear if or how long the children had been living in the sewer, if they had run away from home or were using the sewer to play. The Lakehaven Utility District and Federal Way Public Works Department were unable to answer calls for comment from The Washington Post; the Federal Way Police Department did not have any information publicly available as of late Monday night.

Workers removed the toys, clothes and bed. After Miller talked to the children, they ran, Fox 59 reported. The city is trying to locate them, though according to local news media the boys have not been seen since.

“Unfortunately, Federal Way Police were not contacted until nearly an hour after the contact with the juveniles by Utility personnel,” wrote police department representative Cathy Schrock in an emailed statement to The Post on Tuesday. “There was no identifying information of the persons located that day. FWPD will continue to work with Lakehaven to ensure the area is monitored to ensure the children do not return.”

Update, Sept. 5: Six days after closing the manhole, utility workers gave photographs of the two children to Federal Way police, which then confirmed to KIRO 7 that neither boy was homeless. The children were playing in the sewer, which they called a “fort.”

This post has been updated.