Secret UK defense department documents detailing the destroyer Defender and the British military have been found at a bus stop in Kent, BBC News reported.

One of the documents discusses the likely reaction of Russia to the passage of the vessel through Ukrainian waters off the coast of Crimea on Wednesday.

Another detail is the plans for a possible British military presence in Afghanistan after the completion of the NATO operation under the leadership of the United States.

The government announced that an investigation was underway.

A defense department spokesman said one of the officers reported the loss of classified defense department documents, adding that it would be inappropriate to comment further on this situation.

Nearly 50 pages of documents were found in a damp pile behind a bus stop in Kent early Tuesday morning.

A member of the public, who asked to remain anonymous, contacted BBC News when he discovered the sensitive nature of the content.

Documents relating to the Royal Navy destroyer Defender show that the mission, described by the DoD as an innocent passage through Ukrainian territorial waters, with the ship's cannons covered and the ship's helicopter stationed in its hangar, was carried out in anticipation of an aggressive response from Russia.

On Wednesday, over 20 Russian aircraft and two coast guard ships followed the warship as it sailed off the coast of Crimea.

The Russian Defense Ministry said the patrol ship fired warning shots and the jet dropped bombs in the path of the destroyer, but the UK government rejected this theory, denying that any warning shots had been fired.

The mission has been the subject of high-level discussions as early as Monday when officials speculated about Russia's reaction if the Defender sails close to Crimea, documents show.

After controversy over the Defender mission, documents found in Kent confirm that the destroyer's route was a calculated decision by the British government to show support for Ukraine, despite the potential risks.