Footprints fund preserved in rocks on the coast of England are the earliest human footprints ever found outside of Africa, researchers say.

Scientists from Queen Mary University of London, the British Museum and the Natural History Museum say as many as five people left the series of footprints in mud along the bank of an ancient river estuary more than 800,000 years ago in northeast Norfolk.

The footprints are evidence of the first known humans in northern Europe, researchers including Simon Lewis from Queen Mary's School of Geography said.

Lewis has been working to date the sediments in which the prints were found.

"My role is to work out the sequence of deposits at the site and how they were laid down," he said. "This means I can provide a geological context for the archaeological evidence of human occupation at the site."

Surviving ancients human footprints are rare, the researchers said -- only those at Laetoli in Tanzania, at about 3.5 million years, and at Ileret and Koobi Fora in Kenya, at about 1.5 million years, are older, a Queen Mary University release said Friday.

The researchers said they were able to identify heels, arches and in one case toes in the preserved footprints, left by about five people, including children and adults, the researchers said.