SAN DIEGO >> Charges against a father-son partnership for allegedly smuggling more than $17 million worth of sea cucumbers to the United States and exporting them to Asia sheds light on a growing and lucrative illegal cross-border trade.

David Mayorquin and his father, Ramon Torres Mayorquin, are accused of a scheme to buy the illegally harvested animals from poachers in Mexico’s Yucatan peninsula, pay for them under fake names and underestimate their weight and value to inspectors at San Diego’s Otay Mesa border crossing, across from Tijuana, Mexico. From San Diego, they allegedly shipped the product to Asia, including China, where they are delicacies in Chinese dishes, prized for medicinal value and considered an aphrodisiac.

Border inspectors have spotted smuggled Mexican sea cucumbers for years, but the charges against the Mayorquins and their family business, Blessings Inc. of Tucson, Arizona, are striking for the multi-ton shipments. Authorities say they sell for $300 to $500 a kilogram in Asia, helping explain the draw for poachers and smugglers.

David Mayorquin, who is listed as the company’s chief executive officer in public records, allegedly bought $13 million worth of sea cucumbers, knowing that they were harvested without a permit or out of season, and they sold for $17.5 million. The indictment, filed Wednesday in federal court in San Diego, lists transactions from January 2010 to July 2012.

U.S. Homeland Security Investigations launched an investigation around 2012 after company transactions raised suspicions, said James Plitt, deputy special agent in charge in San Diego. They examined financial and shipping records.

“These cases are very document-intensive,” Plitt said. “The volume of documents that have to pulled together and corroborated is significant.”

Investigators found emails that allegedly show the family communicating with others about the illegal purchases, Homeland Security Investigations said.

“I hope you’re aware that you are asking for 17 tons and we have no papers for that amount since Carlos’ entire product is without invoice,” a supplier wrote David Mayorquin in 2011, which is mentioned in the indictment. “Nearly 10 tons would be traveling without papers.”

The defendants also bribed Mexican officials, prosecutors say. One email listed in the indictment shows Marroquin being asked to contribute $32,000 for payoffs.

Court documents do not list an attorney for the Mayorquins or the company, which was also charged. A woman who answered the phone at Blessings on Friday said the company had no comment and hung up.

Sea cucumbers, which are shaped like cucumbers with small feet and measure up to six feet (1.8 meters), are echinoderms, a family that includes starfish and sea urchin. They are served dried or fresh and often braised with fish, vegetables and traditional Chinese sauces. They are sought to treat join pain, prevent cancer and serve as anti-inflammatory medicine.

Harvesting sea cucumbers is permitted in the United States and many parts of the world, but with limited quantities and only during high season. Blessings was licensed with the U.S. Fish and Wildlife Service to import and export sea cucumber, according to the indictment.

Border inspectors in San Diego screened three large — and legal — commercial hauls in the last week alone, said Erin Dean, resident agent in charge of Fish and Wildlife’s Southern California office. Prosecutors have also fielded a growing load of smuggling cases, which typically involve hiding the animals in vehicles or on bodies, she said.

Totoaba fish, whose dried bladders sell for thousands of dollars to Chinese traders, are also commonly smuggled from Mexico along California’s border. Vaquita porpoises are often caught in the nets, causing their population to drop to about 30.