The red crustacean was first imported for food a few years ago and quickly became a favorite, with restaurants serving crawfish soon mushrooming.

"Crawfish used to cost up to VND1 million ($43) per kilogram at restaurants but thanks to its popularity, prices have dropped to VND250,000-500,000," a Ho Chi Minh City wholesaler named Thoa said.

China and the U.S. in that order are the major exporters of the crustacean to Vietnam.

But agriculture experts are warning this represents clear and present danger.

Dang Huy Huynh, former head of the Institute of Ecology and Biological Resources, said the species could become a "disaster" for both agriculture and the ecosystem and called stopping its import.

"Crawfish feeds on almost all kinds of aquatic species and competes for food with local species, and if they live together in the same environment, it is possible that some local fish or shrimp species could disappear."

Bui Quang Te of the Research Institute for Aquaculture said scientists identified the crawfish as a species harmful to agriculture after a pilot breeding program in the northern province of Phu Tho in 2012.

They reproduce quickly and withstand environmental changes. With their strong claws, they easily cut paddy stalks, feed on many species of young plants and burrow and destroy dykes, he said.

"If crawfish spread across fields in Vietnam, they could spread diseases and viruses that could damage the crops."

China has been having a hard time dealing with the explosion of crawfish in the Yangtze River.

Vietnam put crawfish on the list of foreign species banned from being imported in 2013 and its 2018 Law on Biodiversity prohibits all activities related to raising and distributing the creature.

"But managing the trade in crawfish has been a hard task because usually it is imported into Vietnam in small quantities via minor border gates," Hoang Thi Thanh Nhan, deputy director of the Ministry of Natural Resources and Environment’s Biodiversity Conservation Agency, said.

Between May 12 and 18, border guards and customs officials in Lao Cai Province which borders China seized 945 kilograms of crawfish in seven smuggling attempts at its border gates. All of them have been destroyed.

The agriculture ministry has made an urgent demand to the customs and market management departments and local authorities to strictly enforce crawfish import regulations.

The Penal Code stipulates a fine of VND100 million ($4,270) to VND1 billion and jail terms of up to five years for the import and distribution of invasive species.