Police arrested two men Saturday on suspicion of trying to illegally bring fertilized eggs and sperm of wagyu cattle into China last year.
The arrests in Osaka Prefecture came as the farm ministry is tightening control of wagyu reproductive material amid the rising popularity of the Japanese beef overseas.
As part of a wider investigation into the smuggling of wagyu reproductive material out of the country, the police said Yusuke Maeda, 51, a restaurant owner, and Toshiki Ogura, 64, who is unemployed, are suspected of violating the country's law on infectious disease control.
Maeda and Ogura have admitted to the allegation of attempting to bring the cattle eggs and sperm into China in June 2018 without prior quarantine inspection, the police said.
Chinese authorities prevented Ogura, who traveled by ferry with the sperm and eggs stashed in straw-like containers, from entering the country in July last year as he did not have a quarantine certificate, according to the agriculture ministry.
The case surfaced after the man returned to Japan with the sperm and eggs and made a declaration at the Animal Quarantine Service. The ministry filed a complaint with the Osaka police in January.