NAHA--Okinawa prefectural police are investigating a suspected illegal ride-sharing service that targets U.S. military personnel and is taking business away from legitimate cab drivers, officials said.

Operating unlicensed taxis is a violation of Japan’s Road Transportation Law.

“There would be a high degree of illegality if passengers were paying for transport (through the ride-sharing service),” said an official with the Okinawa General Bureau, which has local jurisdiction over transportation matters.

U.S. military officials said they were aware of the service but did not know who was operating it.

According to those who have used the service, people with ties to the U.S. military opened a Facebook account under the group name of “U-Ride Okinawa.”

Members can use the account to show the time and location of their pickup and destination as well as the number of people in their party.

The vehicles used can carry seven or eight passengers, and all have license plates with the Y letter indicating that the vehicle is for private use by those connected to the U.S. military.

Members of a party split the bill and pay the fare to the driver.

“We are a group of volunteer drivers offering friendly, efficient, and reliable transportation throughout Okinawa for our military community,” the Facebook account states.

The group goes on to explain that it does not employ the drivers, and that all transactions are between the driver and passengers.

The group also states there are no restrictions on the “donation” established between passengers and the driver, and that the group bears no responsibility for any problems that may arise.

As of July 2, the group had 5,597 members.

Okinawa police officials said they became aware of the group’s operations about a month ago and had contacted the U.S. military. From early July, it was no longer possible to use the group’s Facebook account.

In response to questions from The Asahi Shimbun, officials with the U.S. Marine Corps and Air Force said they knew about groups offering ride-sharing services over social media but did not know the identities of the operators.

The officials added that they were aware such activities are illegal in Japan, but that the interpretation of the law was in the hands of Japanese authorities.

“I hope the police crack down on the activities that are clearly interfering with our business,” said a Japanese taxi driver who often transports U.S. military personnel.