U.S. authorities said Monday that they had arrested a Chinese researcher accused of smuggling biological material into the country, the second such case in days.

Two Chinese researchers were charged with smuggling a biological pathogen that they planned to study at a University of Michigan lab, a complaint says.

This is the second case revealed in about a week involving a Chinese academic smuggling biological material into the U.S. A criminal complaint filed Monday alleges Chengxuan Han sent four packages in the last several months.