Security at U.S. military bases in Japan was beefed up this week, but military officials aren’t saying why.

Maj. Jason Medina, a U.S. Forces Japan spokesman, said Wednesday that USFJ and 5th Air Force Commander Lt. Gen. Bruce Wright called a force protection change across Japan.

“We won’t discuss general aspects of the threat,” Medina said, noting local commanders have some latitude to implement changes in accordance with each force protection category.

For security reasons, Medina said USFJ would not comment on whether the force protection change was due to an exercise or potential real world threat.

He also would not say when the change was ordered and whether it had been lifted.

“This is something that he determined to be the appropriate thing to do at the time,” he said of Wright.

Force protection conditions were raised at Camp Courtney on Okinawa last Friday and at Misawa Air Base in northern Japan this week.

There were no change in threat conditions on base at Yokota, Marine Corps Air Station Iwakuni and the naval bases in Yokosuka and Sasebo, base spokespeople said Wednesday.

Sasebo has increased its security “posture” a bit, but it’s all a part of the base’s random anti-terrorism measures, said base spokesman Chuck Howard.

“Terrorism is a reality in this world and we need to be vigilant at all times,” Howard said.

At Yokota Air Base near Tokyo, the shuttle bus service between the base and the New Sanno Hotel in Tokyo has been suspended for force protection reasons, according to Capt. Warren Comer, a base spokesman.

He did not say when the service would resume.

Medina said the order to suspend the service did not come from USFJ or 5th Air Force.

Comer said the shuttle was stopped in response to a high-level Air Force order “to change some of the force protection standards that we have.”

“For the safety and security of the people at Yokota, it was determined we had to stop use of the shuttle bus going to the New Sanno Hotel.”

Comer said he’s unaware of restrictions on any other government vehicles traveling between Yokota and Tokyo.

The base’s Narita shuttle is still running, though it’s skipping the New Sanno and Hardy Barracks in downtown Tokyo and the Tama recreation area, according to Yokota Services.

A Tokyo Metropolitan Police spokesman said Wednesday he knows of no reason — such as an increase in terrorism threats — to prompt suspension of the New Sanno bus.

Base officials at Camp Zama and Misawa said their shuttle bus to Narita airport was running as usual.

Comer noted there are alternate options to get to the New Sanno, such as the train or private vehicle.

“We’ll let people know when the bus starts up again,” he said.

Stars and Stripes reporters Allison Batdorff, Hana Kusumoto and Bryce Dubee contributed to this story.