Boston — Animal rights activists say Northeastern University lab researchers are pitting steroid-injected hamsters against undrugged ones to study aggression.

In a complaint released this week, People for the Ethical Treatment of Animals argues that the experiments violate the state's ban on animal fighting.

The organization says the lab trains hamsters to fight and contributes to a fight atmosphere by injecting some animals with steroids and using others as bait. PETA wants Massachusetts to file charges against lead lab researcher Richard Melloni and others.

Melloni, a longtime researcher, has received millions in federal grants dating back two decades. He says he is unaware of the complaint and declined to comment further.

Northeastern University, in a statement, noted that Melloni's research has been inspected and approved by the U.S. Department of Agriculture and the university's Institutional Animal Care and Use Committee, among other agencies.

State Attorney General Maura Healey's office said it's reviewing PETA's complaint. It did not comment on whether the research lab's work is a violation of the law.