WASHINGTON (Reuters) - US Marines killed in two fighter jets near Japan last year have been involved in unprofessional activities during flights such as reading books, taking selfies and browsing WhatsApp, according to a recent military report.

The two planes, a KC-130 and an F / A-18 Hornet fighter, collided on December 6, 2018, about 200 miles off the coast of Japan's Shikoku Island, killing six Marines.

A preliminary investigation revealed new details of the crash, which showed that neither aircraft had any malfunction before the collision, and the report was partly blamed on the "climate of non-professionalism by the Marines," according to the newspaper "Daily Mail" and the site "Japan Times" "About the report.

According to the report, members of the Marines unit stationed in western Japan removed oxygen masks and aircraft controls to take selfies, and read books.

One pilot was found to have a selfie in WhatsApp during the flight, after removing his oxygen mask, another officer shared a selfie while reading a book with both hands on flight controls, and a third officer shared a selfie while combing his mustache, the report said.

At the time of the incident, the US Marine Corps announced that the two fighter planes that were involved in the crash were a refueling aircraft with five crew members on board. The Japanese Navy rescued two Marines, but one later died of his wounds.