Heathrow Airport says it has launched an investigation after a USB stick containing confidential information was reportedly found on the street.
The stick held a total of 76 folders which included maps, videos and documents as well as the route the Queen takes to the airport, the Sunday Mirror reported.
The USB stick was discovered by a man in west London who subsequently handed it into the paper, it said.
The device had at least 174 documents on it, some of which were marked "confidential" or "restricted" but could be read, said The Sunday Mirror.
A spokesman for the airport told the paper it is "confident that Heathrow remains secure" after it reviewed all of its security plans.
The paper said the stick contains information which includes safety measures to protect the Queen, the type of ID needed to access restricted areas and positions of CCTV cameras.
The paper said it has passed the memory stick to Heathrow intelligence chiefs.
“Heathrow’s top priority is the safety and security of our passengers and colleagues.
In a statement given to the paper Heathrow said: "The UK and Heathrow have some of the most robust aviation security measures in the world and we remain vigilant to evolving threats by updating our procedures on a daily basis.
“We have reviewed all of our security plans and are confident that Heathrow remains secure.
“We have also launched an internal investigation to understand how this happened and are taking steps to prevent a similar occurrence in future."