SINGAPORE — Singapore seized more than 28 tons of pangolin scales belonging to around 38,000 of the endangered mammals in the past week, a global record that spurred calls for more protection for pangolins, whose scales are used in traditional medicine.

The scales were linked to four species of pangolins native to Africa.

A record 14.2 tons of the scales were found hidden among packets of frozen beef in shipping containers on April 3. Five days later, they found 14 more tons in 474 bags in another container. The National Parks Board, Singapore Customs and the Immigration and Checkpoints Authority said in a statement Wednesday that the cargo was declared as cassia seeds. Both shipments were en route from Nigeria to Vietnam.

"The sheer size of these two latest seizures is unprecedented and will undoubtedly prove a major setback to the traffickers concerned," said Richard Thomas of monitoring network Traffic.

He warned that the seizures themselves won't put the traffickers out of business. "The quantities of pangolins involved point to sourcing, processing and distribution on an industrial scale," Thomas said.

The pangolin is said to be the most widely trafficked mammal in the world, and its scales are in high demand in Asia for use in traditional Chinese medicine. The scales are made of keratin, the same material in human fingernails. Their meat is also considered a delicacy in China and other Asian countries.

Wildlife groups are concerned that the busts point to a jump in poaching of pangolins.

"The World Health Organization recently endorsed traditional medicine and the industry appears keen to grow this market, outside of China, Vietnam and beyond," said Neil D'Cruze, the global wildlife adviser at the World Animal Protection. "This is an alarming move for some wildlife species such as pangolins, as it poses a real conservation and animal welfare threat."

Pangolins are an extremely lucrative catch, he said. In rural communities where they're hunted, poachers can make up to the equivalent of a full year's salary from catching just one pangolin. Feeding "the insatiable demand" are middlemen traffickers who also profit from the trade that's reaching more remote communities to hunt the animal, he added.

Paul Thomson, an official at the Pangolin Specialist Group, said it looks like the pangolin poaching has increased but figures were difficult to ascertain.

"The illegal trade in pangolin parts has been going on for decades. However, pangolins have typically been overlooked in terms of concerted conservation attention and action," Thomson told The Associated Press. "This is changing thanks to growing awareness of pangolins. And this awareness has partly been driven by the high volumes of trafficking seen today."

In February, Malaysian officials seized 30 tons of pangolin and pangolin products. This included live and frozen pangolins and 361 kilograms (795 pounds) of their scales.

Earlier that month, Hong Kong said it had seized ivory tusks and 8.3 tons of pangolin scales belonging to as many as 13,000 pangolins. The shipment, which originated in Nigeria, was bound for Vietnam.

Singapore made two markedly smaller pangolin scale busts in 2015 and 2016 amounting to 440 kilograms (970 pounds). Those found to have illegally imported, exported or re-exported wildlife, including their parts, face a maximum punishment of two years in prison and a fine of 500,000 Singapore dollars ($367,000).

"There has never been a more opportune moment for full and thorough international investigations and collaborations to take place to find out who has perpetrated these criminal acts and bring those behind them to face justice," Thomas said.