TOKYO (AP) — Japanese police said they were investigating a possible attack on a U.S. Army base near Tokyo after finding a pair of launchers and a projectile Tuesday following reports of explosions in the vicinity.

Two iron pipes planted into the ground and aimed at Camp Zama were found about 800 meters (half a mile) southwest of the base, which sits near a residential area and an elementary school, police said. No injuries or damage were immediately reported from the incident.

Police found the pipes after a resident reported hearing three explosions in the area in the early hours of Tuesday.

Investigators later found a projectile at another field nearby that was believed to have been fired at the base from one of the launchers.

Police said they were investigating the incident.

Prime Minister Shinzo Abe is on a weeklong tour of the United States, where the two sides agreed late Monday to a revision of defense guidelines that would boost the Japanese military’s role in bilateral cooperation amid China’s growing assertiveness in the Asia-Pacific region.

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