The U.S. Navy said Thursday it is investigating several crew members of the aircraft carrier Ronald Reagan home-ported in Yokosuka, near Tokyo, over suspected involvement in drug use and drug trafficking.

"We take all reports of misconduct seriously, and are working with the appropriate Japanese law enforcement agencies," a Navy official said. The investigation is in the initial stage and it was not immediately clear what type of drug was used and the number of people involved.

The Ronald Reagan is believed to have departed from its base on Tuesday for a long-term patrolling mission.

In 2018, a U.S. Navy sailor assigned to the Ronald Reagan was referred to Japanese prosecutors for allegedly smuggling narcotic drugs by international mail.

Photo taken May 12, 2023, shows the U.S. Navy aircraft carrier Ronald Reagan departing from Yokosuka base in Kanagawa Prefecture, eastern Japan. (Kyodo) ==Kyodo