MEXICO CITY (AP) — Authorities said Monday a zoo employee who was killed by a lion in central Mexico may have forgotten to shut a gate that separated the animal's feeding and sleeping areas.

Mexico's office for environmental protection said an inspection of the enclosure showed no holes or breaches where the animal could have escaped.

"The incident could have been caused by human error, like a lack of precaution by the zoo employee who presumably forgot to close the door from the outside," the office said in a statement.

The lion was being held with a lioness at the Nicolas Bravo zoo in Tulancingo, northeast of Mexico City.

The zookeeper was killed by the animal on March 17 as he cleaned the enclosure. Authorities fired tranquilizer darts but were unable to stop the attack.

Also on Monday the office said inspectors found two young lions being kept at a private home in Mexico City.

Photos showed one of the lions on the home's patio, with a metal gate separating it from the street.

Inspectors seized the animals on the grounds that the person keeping them did not have legal documents showing where they came from.