German police are searching 16 homes of alleged Islamic extremists in central and western Germany.

Frankfurt prosecutor Nadja Niesen said Thursday that authorities were acting on the suspicion that the extremists were planning an attack. Niesen said she could not give any further details because the searches were still ongoing.

Authorities raided 15 homes Thursday morning in Ruesselsheim, Biebesheim, Raumheim in the state of Hesse as well as one home in Kerpen in North Rhine-Westphalia.