PHOENIX — Some metro Phoenix residents have been rattled by low-flying helicopters in their neighborhoods, including a particularly loud incident Thursday night.

But police say there’s no cause for concern: the military choppers are part of a two-week U.S. Special Operations training exercise that the Phoenix Police Department had previously announced.

Police closed down roads around Jefferson and Washington streets for safety Thursday night. A black helicopter hovered around the Sandra Day O’Connor U.S. Courthouse while crews exited the aircraft and landed on the roof of a federal building.

Spokesman Sgt. Jonathon Howard says such activities are planned months in advance.

Police say the training has taken place across the Phoenix metro this week and is expected to last through Saturday.