German federal authorities said on Wednesday that four people have been arrested for plotting to attack mosques and immigrant housing centers, the Associated Press reported.

Federal prosecutors said in a statement that three men and a woman accused of being members of a far-right extremist group were arrested, and that about 250 investigators had searched homes in Saxony and four other states.

The so-called “Old School Society” was planning to attack housing centers used by asylum seekers, mosques and prominent Salafist Muslim figures across Germany.

The four, identified only as Andreas H., Markus W., Denise Vanessa G. and Olaf O., are accused of founding the group, and acquiring explosives to use in their plot.

Prosecutors say they are not yet aware if they had any specific attack plans yet.