TOKYO — Two metal pipes believed to be mortars were found Thursday evening near Yokota Air Base, according to a local Japanese police spokesman.

Police patrolling outside the base in Fussa found the devices — two 4-foot-long metal pipes with wires attached — around 7:10 p.m. outside a garden center about 300 meters west of Yokota’s main gate, the spokesman said.

Police found no signs that projectiles were launched. No injuries or damages were reported, the spokesman said.

The police declined to reveal any information about suspects, saying the case is an ongoing investigation. No one has claimed responsibility, he said.

Yokota officials are cooperating with the local police, according to base spokesman Maj. Christopher Watt.

Blasts by similar mortars have been reported near the U.S. military bases in the Kanto area in recent years, including at Yokota, Naval Air Facility Atsugi, Camp Zama and Yokosuka Naval Base.

Last year, a mortar round punched a hole in the balcony of an off-base home in Yokosuka. A group that claimed responsibility said it was protesting the arrival of the USS George Washington, a nuclear-powered aircraft carrier, to the base.

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