New photographs and video exclusive to National Geographic suggest that two dozen young elephants flown to China from Zimbabwe in July are being mistreated and are slipping into poor health, according to analysts who have examined the images.

The elephants—many no more than two or three years old—are being held in at the Qingyuan quarantine facility in Guangdong Province, awaiting transfer to Chimelong Safari Park, also in Guangdong.

In late 2014, the elephants were taken from their mothers and families in Zimbabwe’s Hwange National Park, where they were held in a capture unit before the airlift.

WATCH: Twenty-four elephants imported to China over the summer showed signs of distress, according to Joyce Poole, an elephant behavior specialist. Video courtesy Nature University

Several conservation and animal welfare groups have decried the export and confinement of the youngsters—wild animals recognized for their high intelligence, emotional capacity, and cooperative nature. The concerns about the elephants—and about the Zimbabwe’s controversial decision to capture the animals and sell them to Chinese interests—come at a time when elephants across sub-Saharan Africa increasingly are threatened by poachers who often kill elephants for their ivory, which is particularly coveted in Asia.

The images of the elephants were taken surreptitiously by Chunmei Hu, a project manager with Nature University, a Beijing-based organization. She has gone into the quarantine facility twice during the past three months to take pictures and video of the elephants. Her first foray went without incident. But the second time, she says, she was caught by security guards and taken to the local police station. Officers demanded her camera’s memory card, but she refused to give it up. She was later released, and the images were made available to National Geographic.

View Images It’s clear, said Blais after reviewing images of the elephants, that the animals aren’t getting medical treatment for their injuries. “Every day,” he says, “they’ll become less and less who they are supposed to be.” Photograph by Nature University

View Images Two young elephants, around four years old, greet one another. According to Joyce Poole, cofounder of ElephantVoices, a research group in Kenya, says the elephant on the right has a swelling on her abdomen that “could be caused by an infection. In the wild, we see such swellings on elephants when they have a spear or arrow wound, or sometimes, after giving birth.” Photograph by Nature University

View Images Seven of the elephants mill about under a netting, which may be intended to provide shade. One of the handlers walks away carrying a long pole used to discipline the elephants. According to Poole, the elephant in the foreground is watching him with a mixture of aggression and fear. Photograph by Nature University

View Images This elephant, taken from her mother in the wild in Zimbabwe months ago, may not be even two years old, Poole says. Photograph by Nature University

National Geographic asked Joyce Poole, who is widely viewed as the world’s leading elephant communication specialist and is co-founder of ElephantVoices, a Kenya-based research and advocacy group, to review the video and photos. Poole said that what’s happening to the elephants is “tragic and morally reprehensible.”

She said the elephants appear to be struggling physically and mentally. They’re “pushing, shoving, and tusking each other, and this is likely the cause of the larger abscesses and open wounds that are visible on a number of elephants.”

According to Poole, this abnormal behavior “is caused by their being held captive without adequate space and without older elephants to protect them and to intervene in disputes.”

Hu’s video appears to show two men with long poles scaring three calves from their outdoor pen into the adjoining indoor enclosure.

Scott Blais, CEO of the Global Sanctuary for Elephants, a Tennessee-based organization that aims to create a network of refuges for captive elephants, also analyzed the photos.

Blais said it appears that the elephants’ wounds aren’t being treated. He noted that urine and fecal stains are present on every elephant. “Due to their small confines,” Blais said, “it’s impossible for them to escape their own waste at night.”

Officials in China have declined to comment. But on Thursday, China’s Xinhua News Agency released photographs of about half of the animals at Chimelong. The elephants appear to be in better shape than those in Chunmei’s images. Caption information supplied by Xinhua said that “24 African elephants were imported from Zimbabwe … as a part of (an) international African elephant conservation program.”

On Friday, China President Xi Jinping and U.S. President Barack Obama made a joint pledge to try to end the ivory trade, the White House announced. The move followed Xi’s announcement in May that China would crack down on that country’s domestic ivory trade.

Export of elephants is sanctioned under the Convention on International Trade in Wild Species of Fauna and Flora (CITES), as long as the trade of individual animals or plants doesn’t threaten the long-term survival of the species. (See “Why It’s So Hard To Stop Zimbabwe’s Export of Baby Elephants”).

Zimbabwe officials have justified the sale of elephants to China on grounds that Hwange National Park has too many elephants and that it’s a way to help fund its impoverished park system.

View Images The grass at the center of the enclosure is too short to provide forage, Poole says, and there are no other signs of food for the roughly 14 elephants here. “They’re all gravitating to the edge of the enclosure where tree trunks provide shade and protection for grass to grow.” Photograph by Nature University

View Images According to Poole, the skin of these elephants looks in poor condition. A couple of elephants’ tusks appear to have broken off at the lip. “This is highly unusual for young elephants, and I am curious to know the cause,” she asks. “Possibilities? Fighting with one another? Breaking them on the bars of the enclosure? Damage during shipment?” Photograph by Nature University

Poole acknowledged that the capture and international trade of limited numbers of elephant calves doesn’t endanger the species as a whole.

But, she said, “it certainly causes enormous and life-long suffering to individual elephants. What are we, the international community, going to do to stop this outright cruelty that is being sanctioned by an international treaty? We need to either revamp CITES or start a new organization that will.”

Zimbabwe exported eight elephants to China in 2012, according to the CITES database.