An American graduate student working as a wildlife ranger at Jane Goodall's famous animal sanctuary in South Africa is in critical condition after a pair of chimps dragged him for almost a half-mile in a "frenzied" attack, the Telegraph reports.

The attack occurred at the Jane Goodall Institute Chimpanzee Eden near the city of Nelspruit in eastern South Africa, the British newspaper reports.

Update at 2:55 p.m. ET: David Oosthuizen, Jane Goodall Institute executive director, said in a statement that the sanctuary is closed temporarily while the tragedy is being investigated.

"This is a terrible tragedy that should never happen," he said. "All our thoughts and prayer are with this young man and his family."

The statement also noted that chimps "are wild animals and are defensive of their territories."

"Any interaction between humans and wild animals can be dangerous as wild animals are often very strong and can act aggressively if approached or if they feel threatened,"he wrote. "Additionally, the chimpanzees at Chimp Eden have suffered horrible injuries and abuse from humans, and therefore have to be treated with caution."

Update at 2:31 p.m. ET: The University of Texas at San Antonio confirms that the name of the victim as Andrew Oberle, an anthropology graduate student, the San Antonio Express-News reports.

Oberle is listed in critical condition and lost several fingers and part of his ear in the assault.

Update at 1:16 p.m. ET: Edwin Jay, chairman of the Jane Goodall Institute South Africa, said the man had crossed the first of two fences separating the chimpanzees from visitors and was standing close to the second fence, which is electrified, at the time of the attack.

Jay said the two chimpanzees involved were part of a group that had been rescued from Angola and brought to South Africa more than a decade ago. He said they were placed in their night enclosure and would be held there while sanctuary officials investigate what led to the attack and confirm the fencing is safe. Then they will be returned to the enclosure.

Original post: The South African newspaper Beeld identifies the victim as Andrew Oberle, a graduate student in anthropology and primatology at the University of Texas-San Antonio.

The newspaper says Oberle lost some fingers and part of his ear in the attack. Reuters reports that the victim lost several fingers when he was attacked by two male chimps, named Mickey and Amadeus.

Paramedics said the man, in critical condition, suffered serious wounds and multiple bites.

The Telegraph quotes Jeffrey Wicks, a spokesman for a private ambulance firm, as saying the man was attacked close to a fence while leading a tour group.

"According to eyewitnesses, two chimpanzees grabbed the man by his feet and pulled him under the perimeter fence and into the enclosure," Wicks says.

The Telegraph quotes David Oosthuizen, Jane Goodall Institute executive director, as confirming the attack and putting the reserve on lockdown.

Oosthuizen is quoted as calling the incident "very upsetting" and "just horrific."

The sanctuary, which conducts daily tours, is home to 33 chimpanzees in large enclosures, the newspaper says.

Reuters says Chimp Eden is a sanctuary for ill-treated chimpanzees rescued from the illegal pet and bushmeat trades and from the entertainment industry. It describes the reserve as a joint venture with the ape conservation institute founded by Goodall, the famed U.S. primatologist. Update and correction: Goodall, of course, is a British primatologist.