TALLINN, Estonia (AP) — A worker at a wildlife park in Crimea died Wednesday when she was attacked by lions, officials said.

According to the Russian Investigative Committee’s office in the Russia-annexed peninsula, the death occurred when the worker went into a cage at the Taigan park to clean it. The cage held three lions, but the worker did not lock an internal door that would have separated her from them, the committee said in a statement.

The Taigan park is in Belogorsk, about 35 kilometers (22 miles) east of the Crimean capital Simferopol. Russia unilaterally annexed Crimea from Ukraine in 2014, but most of the world does not recognize it as Russian territory.

According to the park’s website, it holds about 60 lions in its more than 30 hectares (75 acres). About 1 kilometer (0.6 miles) of elevated walkways allow visitors to observe lions roaming freely.

The investigative committee said it has opened a criminal case on possible negligence charges, but it was not clear if the park or the worker were negligent.