The body of a dead man has been found on the roof of a London shop on Thursday believed to have fallen from a British Airways flight from Johannesburg.

British police said on Friday, another suspected stowaway is currently being treated in a London hospital after being found unconscious on the plane.

The man found alive is believed to be between 25 and 30 years old and was "unconscious and remains in a serious condition," a police spokesman told AFP.

The spokesman could not say where the man was found.

He added that the possibility that the two men were on the same plane is "one of the lines of inquiry".

The police were called about the suspected stowaway on the 8,000-mile (12,875-kilometre) flight from South Africa at 8:28 am and about the body at 9:35 am.

A British Airways spokeswoman said: "We are working with the Metropolitan Police and the authorities in Johannesburg to establish the facts surrounding this very rare case".

In 2012, a man from Mozambique fell from the undercarriage of a Heathrow-bound flight from Angola onto a street under the flight path in west London.

An inquest found that he may have survived freezing temperatures for most of the flight but was "dead or nearly dead" by the time he hit the ground.

There have been several cases of stowaways being found dead clinging to the landing gear of planes.

In April, however, an Indonesian stowaway survived an hour-long flight from Sumatra to Jakarta.