Officials at the Auschwitz-Birkenau Memorial and Museum — on the sites of the two camps where more than one million people died during World War II — said they had been caught off guard and had no idea what was intended.

Malgorzata Jurecka, a spokeswoman for the district police office in Oswiecim (Auschwitz is the German spelling), said late Friday that 11 people were detained — six Poles, four Belarussians and one German. “At the moment, we are gathering and securing all the evidence connected with this case to determine the exact involvement of the individuals in this dramatic incident,” she said. “It was macabre.”

Museum officials take a dim view of groups using the site as a backdrop for political statements. “Using the symbol of Auschwitz for any kind of manifestations or happenings is outrageous and unacceptable,” the museum said in a statement. “It is disrespectful to the memory of all the victims.”