Yokota Air Base officials and Japanese police are investigating a suspected mortar launch Wednesday night at the base.

Base and local Japanese residents reported seeing two arcs of light accompanied by loud bangs at about 10 p.m. Police authorities, however, said the explosion occurred near 11 p.m.

No injuries or damage was reported on the base, according to Yokota spokesman Air Force Capt. Michael Braibish.

“We found nothing on the bases yet,” Braibish said at about 8:30 a.m. Thursday. “We’re doing an extensive search, conducting the operations right now.”

A Fussa police official told Stars and Stripes they found two barrels partially buried in the ground at a construction site about 328 yards west of the base. The official said the barrels were pointed toward Yokota.

They reported no injuries or damage off-base.

No suspects have been identified and no groups have claimed responsibility, police said.

Japanese investigators were mulling over the scene Thursday morning in a neighborhood dotted with mostly two-story houses. A construction site lined with discarded building materials and derelict cars filled with junk was taped off.

Several buses filled with Japanese police entered through the main gate around 9:30 a.m. presumably to begin searching the area just inside the base for evidence.

Braibish declined to discuss security measures the base is taking, but he said some measures include working with the Japanese National Police to secure the perimeter and an area outside the perimeter fence. Operations are continuing at a normal level at this time, he said.

“We’re confident we have reached a position where we’ve ensured the safety and security of the people on this base and we will continue to work with the Japanese police to protect Yokota and carry the investigation forward,” Braibish said.

Police believe the mortar launch is connected to similar launches in November when projectiles and launchers were found near Camp Zama and Japanese Self-Defense Forces garrison in Tokyo.

They said the incidents are similar because of the time of day, the type of launcher and they were aimed at military installations.

On Nov. 18, Japanese police investigated the launch of a projectile recovered after flying some 900 yards over the U.S. Army Japan headquarters at Camp Zama before it struck a house near the camp.

Two mortar-like launchers were later found next to a private cemetery in a densely wooded area near the camp. No one claimed responsibility for the incident.

Similarly, on Nov. 20, two metal pipes were found outside of the JASDF garrison in Tokyo around midnight.

Yokota Air Base and other U.S. Forces bases in the Tokyo area have been occasional targets of projectile launches.

In July 1993, Zama was again the target of two projectiles fired, including a 12-inch cylindrical metal shell that hit the ground near the camp’s fire station.

A hole 4 inches in diameter was later found in the ground near a pine tree 100 yards from Zama’s front gate. No one was injured.

A pair of projectiles were fired toward Yokota Air Base from the northeast perimeter of the base with one projectile landing near the runway, Air Force officials reported in July 2000.

Japanese police said anti-military radicals or leftists radicals opposed to an upcoming Group of Eight economic summit in Tokyo were suspected.

A homemade rocket exploded in mid-air as it flew towards Yokota in July 1993, but fell harmlessly short of its intended target.

Police believed it may have been the work of the same leftist radicals who in 1986 fired similar weapons at Yokota three weeks before the 1986 G-7 economic summit held in Tokyo.

No injuries were reported in any of the incidents.

— Jennifer Svan, Hana Kusumoto and Wayne Specht contributed to this report.

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