An investigation is underway in Germany this week after anti-immigration protesters hurled tomatoes at German Chancellor Angela Merkel during a campaign event in southern Germany.

Police said at least two tomatoes were thrown at Merkel during her speech at a campaign rally Tuesday, with one hitting her left hip, leaving a stain on her signature jacket, and another one hitting the event’s moderator, Germany’s DPA news agency reported.

The rowdy demonstration occurred during Merkel’s first campaign stop of the day, a 40-minute rally in a small university town that attracted about 3,000 people, Bloomberg News reported.

Merkel is seeking a fourth term in the Sept. 24 parliamentary elections, where her Christian Democratic Union (CDU) party is expected to win, the latest polling suggests.

A small group of instigators blew whistles and shouted at Merkel during her speech -– protesting Merkel’s policy of open borders that led to the arrival of at least 1 million unvetted migrants into the country.

The demonstrators were heard calling the German leader a “liar” and “betrayer of her people.”

During the speech, Merkel celebrated people who helped the new arrivals during the 2015 migrant crisis, calling it a “grand piece of humanitarian aid,” according to DPA.

The chancellor added: "If we made a mistake, then it wasn't in taking in people, but rather that we didn't pay attention to the fact that people in Jordan, Lebanon, Turkey and Syria didn't have enough to eat, weren't getting an education and put themselves into the hands of people-smugglers.”

This was not the first time Merkel has faced protesters during a campaign event over her immigration and refugee policies. She previously said that right-wing demonstrators “can only shout,” Bloomberg reported.

Following Tuesday's incident, Merkel attended a panel discussion in another city. She wore the same stained jacket at other events on that day, DPA reported.