This is an archived article and the information in the article may be outdated. Please look at the time stamp on the story to see when it was last updated.

WASHINGTON (AP) — Zookeepers at the National Zoo made a macabre discovery this week, when they entered the outdoor enclosure that housed 74 flamingos. A wild fox from neighboring Rock Creek Park had apparently chewed a hole in the metal mesh fencing and wreaked havoc, killing 25 flamingos and injuring three others. One Northern pintail duck was also killed.

Brandie Smith, the zoo’s director, called it “a heartbreaking loss for us and everyone who cares about our animals.” Smith said in a statement that the fencing and other protective measures were being assessed and upgraded to prevent similar break-ins.

“Our focus now is on the well-being of the remaining flock and fortifying our habitats,” she said.

The birds, formally known as American or Caribbean flamingos, are instantly recognizable from their long stilted legs and distinctive pink hue. Those at the zoo have their wings clipped and could not fly away from the predator. The remaining flamingos have been moved to an indoor enclosure and the injured birds are being treated by the zoo’s veterinary staff.

The Zoo’s Bird House is currently closed to the public for long-term renovations, and the flock mainly lives in a 9,750-square-foot yard with a barn and a heated pool. Zoo officials said the area was last inspected on Sunday around 2:30 p.m.

When staff returned early Monday morning, they found more than two dozen dead birds and a “new softball-sized hole in the heavy-duty metal mesh that surrounds the outdoor yard,” according to an official zoo statement.

Zoo staffers also briefly spotted the fox in the outdoor area, but the animal escaped.

The mesh fencing is specifically designed to prevent being chewed through by predators, and “dig barriers” are also there to block any attempt to burrow under the fence. The fencing was last replaced in 2017 and had passed all previous safety inspections.

This week’s attack is the worst such incident at the zoo in 20 years. In 2002 and 2003, a string of animal raids — also by foxes — led to the deaths of more than a dozen ducks, a peacock and an elderly bald eagle. Zoo officials instituted new security measures in response to those attacks, and those barriers have largely held firm until now.

Now the zoo is boosting security again — reinforcing the mesh barriers, setting live traps around the outdoor yard and installing movement-triggered cameras to photograph any nocturnal activity.