UC Berkeley police are investigating the theft of names and emails of people interested in joining the Berkeley College Republicans, the student group whose invitation to Milo Yiannopoulos of Breitbart News prompted a night of student protests and anarchist mayhem last week.

The Republicans had their usual table set up on Sproul Plaza at noon on Feb. 2, the day after the forced cancellation of the Yiannopoulos talk, when someone approached and took the signup sheet, said Sgt. Sabrina Reich, spokeswoman for the campus police, who received a formal complaint about it on Saturday.

Although members of the Republican group recovered the signup sheet, “the individual took a photo of the list and fled the area,” Reich said.

Later, people on the list received “harassing emails” asking about their attendance at the Yiannopoulos event and warning of “negative repercussions,” such as making their names and addresses public, Reich said.

Meanwhile, a blogger who opposes Yiannopoulos and the student Republicans has posted the list on the Web. The Chronicle is not linking to the blog post because the students identified on the list haven’t agreed to make their names and emails public.

The post says the blogger received the list from the person who snapped a photo of it.

Leaders of the Berkeley College Republicans did not respond to requests for comment.

The group’s treasurer, David Craig, is quoted in the Daily Californian, the campus newspaper, saying that whoever stole the list is “attempting to extend their harassment of Milo to our potential members, and that’s an underhanded thing to do.”

Campus police offered to post an officer beside the Republicans’ table, but the group has canceled its tabling lately because of rain.

Meanwhile, police are waiting to see if more emails arrive, and are “looking at all the recent incidents to see if it may generate any leads,” Reich said.

Nanette Asimov is a San Francisco Chronicle staff writer. Email: nasimov@sfchronicle.com Twitter: @NanetteAsimov