The incident happened at about 5 p.m. when a parachutist on a training mission from Yokota cut away his chute mid-flight and landed safely on the base, a statement from the 374th Airlift Wing said.
"A piece of parachute equipment was found off base at Hamura No. 3 High School, and there were no reported injuries or damage," the statement said.
The incident follows protests by Japanese residents over U.S. military aircraft parts falling onto schools on Okinawa and the arrival of CV-22 Osprey tilt-rotor aircraft at Yokota last week.
"Yokota Air Base takes matters of this nature seriously and the incident is under investigation," the statement said.