The Harvard University Police Department denied allegations that the University maintains an undercover political intelligence unit in the wake of two arrests that attracted the scrutiny of the American Civil Liberties Union.

“Despite what the ACLU asserts, we do not maintain an undercover unit,” HUPD spokesman Steven G. Catalano wrote in a statement Monday. But a police report does show evidence of undercover intelligence gathering at a political demonstration.

“I had been photographing the demonstrators for intelligence gathering,” Detective Thomas F. Karns Jr. wrote in a March 3 report of his activities at a human rights protest in the Square. He described himself as “conducting plain clothes surveillance on a demonstration.”

Lisa M. Nieves and Patrick J. Keaney were arrested by Karns after the protest.

ACLU attorney John Reinstein, who is representing Keaney, said that the ACLU has filed a Freedom of Information Act request to see if Harvard is sharing the intelligence it gathers with the federal government, specifically with the joint terrorism task forces overseen by the FBI.

The task forces are local units of law enforcement and intelligence officials based in cities around the country, including Boston. According to Reinstein, several universities work with these special groups, including the University of Massachusetts, the University of Texas, the University of Georgia and the University of Arkansas.