Updated

A British zoo is accused of hiding a penguin massacre at its facility after it left a sign claiming alterations were being done at the enclosure -- only to announce weeks later a fox had sneaked in and killed the birds.

Chessington World of Adventures, south of London, announced on Tuesday an urban fox "infiltrated" Penguin Bay in June, killing five adult and three infant Humboldt penguins. Another male penguin was injured, but has since made a full recovery.

"We are investigating why this happened as Penguin Bay was only built in 2015 and had special measures put in place specifically to deter foxes, and therefore we are shocked and saddened by this news," Lisa Britton, the assistant zoo manager, said in a video posted on the Facebook page.

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However, for weeks the zoo explained the closing of the popular exhibit as being for "alterations" to the area.

A statement on the Chessington website stated: "Our Humboldt Penguins are currently enjoying their other home behind-the-scenes while we make alterations to Penguin Bay."

A source also told The Telegraph that security and zoo staff were not monitoring the enclosure when the attack happened in June.

Workers were allegedly also not allowed to talk about the penguin massacre.

A zoo spokeswoman vehemently denied the claims to the news site, saying they had no obligation to reveal what happened to the dead penguins.

"It’s a fine line between alerting our guests, because some of our animals do die, and actually it’s not something our zoo license says we have to do," she told the site. "It’s certainly something we never hid from any of our guests, our penguins were our number one priority."

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The rest of the 20 penguins in the enclosure were removed to a "secure area" as the staff renovates the space to prevent another fox from lurking in, according to Britton.

"The health, safety and welfare of our animals is the primary concern to us here at Chessington World of Adventures Resort," she said.