BERLIN (AP) — Police in Berlin are investigating a suspected arson attempt early Monday at the office of an Iranian opposition group.

Members of the group noticed flames at a window of the building in Berlin’s Schmargendorf district at about 2:15 a.m. and were able to extinguish them before they spread inside, police said in a statement.

No one was hurt, and a police investigation was under way. The statement didn’t give further details or say who might have been responsible.

The group, the National Council of Resistance of Iran, claimed that assailants affiliated with the Iranian government “initiated the attack by throwing incendiary materials towards the building.”

The NCRI is the political wing of the Mujahedeen-e-Khalq, which is considered a terror organization by Iran and was once designated as such by the United States until it was delisted in 2012. The EU removed the group from its terrorism list in 2009.