The government has launched an investigation into the British defense documents that were left at the bus station.

A batch of classified British defense documents was recently found at a bus stop in England, including the contents of British destroyer operations off the Crimea, which also triggered a warning of Russian fire. The British government said today that it has launched an investigation into the leak of the documents.

An unnamed member of the public told the BBC on 22 June that they found 50 pages of classified documents at the back of a bus station in Kent, southern England. The documents discuss actions like the British destroyer HMS Defender sailing in Ukrainian territorial waters in the Black Sea off Crimea on the 23rd, which may have triggered a Russian response, the newspaper said.

The U.K. Ministry of Defense said it has launched an investigation after an employee notified the ministry last week that a batch of documents were missing.

Speaking to Sky News today, UK Secretary of State for Northern Ireland Brandon Lewis said: “This should not have happened. The appropriate notifications were made at the time… There is an internal investigation into the circumstances of the incident.”

Russia’s Defense Ministry said on the 23rd that it had fired a warning shot at the British ship Defender, which had intruded into territorial waters that day. For its part, Britain said at the time that the Defender was conducting an innocent passage in Ukrainian territorial waters in accordance with international law.

According to Moscow, the incident took place off Cape Fiolent in Crimea. Russia annexed Crimea from Ukraine in 2014, but the international community overwhelmingly does not recognize Crimea as Russian territory.

The seized British defense documents appear to show that British officials were previously aware that the Guardian’s route could lead to a Russian response, but that diverting the British ship could be interpreted by Moscow as “British fear/flight.

Another part of the document also states that the final route taken by the Defender “provided an opportunity to interact with the Ukrainian government and… within UK-recognized Ukrainian territorial waters.”

The Russian Foreign Ministry summoned the British ambassador to express its “strong protest” against the frigate’s incursion on the 24th. Kremlin spokesman Dmitry Peskov also described it as a “deliberate and premeditated provocation”.