A zookeeper at the Madrid Zoo has been seriously injured after a gorilla entered a locked area.

The zoo said in a statement that the 46-year-old officer went to the “triple-door border area” at 10.15am on Sunday for regular feeding and cleaning. They attacked a 29-year-old animal named Malabo.

“The reasons why the animal was able to enter the area are being investigated internally,” a statement from Facebook said, adding that there was a criminal investigation.

Before a veterinary team anesthetized Malabo, they were able to “remove the animal” from an area that was believed to be used for driving by other workers and inaccessible to the public.

The statement said Malabo had been taken to a sleeping area and was currently calm.

The caretaker, who has worked there for 19 years, wished the zoo a speedy recovery.

According to local media reports, the worker suffered head injuries, chest pains, multiple fractures and broken both arms.

Malabo weighs 200 kg (440 lbs).

Videos posted by Madrid Emergency Services show paramedics carrying stretchers, and ambulances and police cars were at the scene.

Madrid police have launched an investigation.