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.

Federal authorities arrested a Chinese researcher connected to the University of Michigan, marking the third such case in two weeks involving the alleged smuggling of biological materials from China.

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