The parents of two small children who were found trapped inside makeshift cages that were bolted to the wall of a Northern California home have been arrested, authorities said Monday.

The grim discovery was made while deputies served a search warrant at a residence in the 3000 block of C/R 101 on Sunday afternoon, according to a news release from the Modoc County Sheriff’s Office.

The warrant was obtained after shell casings were found on the property when a CHP officer visited to sign off on a correctable citation, television station KRCR in Redding reported.

Authorities had no idea there were children in the home when they went to search it, Sheriff Tex Dowdy said, according to the station.

Both kids were found in two separate modified cribs, one stacked on top of the other. The cribs were “secured to the wall like dog crates,” the release read.

The twin boys are believed to be about 22 months old, KRCR reported.

A search of the home also uncovered three firearms, ammunition, suspected methamphetamine and evidence of a butane honey oil lab, according to the release.

It’s still being investigated why the boys had been locked up, but Dowdy told the station he suspected “it was a way to keep them away from the other items that were located within the residence.”

Ramon Alberto Zendejas, 25, and his girlfriend Mercadies Irene Williams, also 25, were both arrested and face several charges, according to the release.

Zendejas was booked on suspicion of being a prohibited person in possession of firearms, a prohibited person in possession of ammunition, possession of a controlled substance, possession of drug paraphernalia and child endangerment, sheriff’s officials said.

Williams was booked on suspicion of being a prohibited person in possession of firearms, a prohibited person in possession of ammunition and child endangerment.

They are each being held on $10,000 bail.

The two children have been taken into the care of Modoc County Child Protective Services, according to the Sheriff’s Office.