The action follows a BBC report that the papers were found at a bus stop in Kent, in the south-east of England.
“The Defense Ministry was informed last week of an incident in which sensitive defense documents were recovered by a member of the public,” the spokesperson told CNN on Sunday in a statement.
“The department takes information security very seriously and an investigation has been opened. The affected employee reported the loss at the time.”
The BBC reports that documents found at the bus stop discuss Russia’s likely reactions to the HMS Defender passing by on Wednesday.
When asked about the contents of the documents relating to the HMS Defender, the Defense Ministry spokesperson told CNN: “As the public would expect, the Defense Ministry plans carefully. analysis of all potential factors affecting operational decisions.
“HMS Defender made an innocent passage through Ukrainian territorial waters in accordance with international law. “
The lost documents also reportedly discussed a possible British military presence in Afghanistan following the end of the NATO mission there. CNN cannot independently verify the content of documents. The Defense Ministry made no comment on Afghanistan when contacted by CNN.
British Secretary of State for Northern Ireland Brandon Lewis called the incident a “serious security breach”, speaking on the BBC’s Andrew Marr program on Sunday.
“To a certain extent the processes were followed; this was reported by the individual as soon as he knew he had left these documents and obviously someone handed it over to the BBC, but there will be a full Department of Defense investigation into how this happened, ”Lewis said.
“We have to make sure that when things like this happen, whether it’s human error or whatever, it can’t happen again.”