In this July 8, 2017 file photo, a young woman with the World Wildlife Fund carries a papier mache replica of the critically endangered porpoise known as the vaquita marina, during an event in front of the National Palace in Mexico City. Researchers in Mexico were thrilled to have captured one of the few remaining vaquita porpoises on Saturday, Nov. 4, but the adult female died after a few hours in captivity in a floating pen, raising questions about the last-ditch effort to enclose the world's smallest porpoises to save them from extinction. (AP Photo/Rebecca Blackwell, File)

Calls are mounting for the Mexican government and international experts to stop an operation to capture and enclose the few remaining vaquita porpoises, after one of the animals died soon after being caught over the weekend.

Experts have always acknowledged the program known as Vaquita CPR would be risky.

On Monday, the experts issued a statement saying Vaquita CPR scientists will work with an independent review panel and the Mexican government to review what happened and "determine how best to proceed."

The Animal Welfare Institute is calling for an immediate halt to the involving the endangered porpoise species. It says that "these tiny porpoises do not respond well to the stress of capture, and not a single additional should be deliberately put in danger in this way."