Lahun's most recent discovery may predate this coffin by 1,000 years
An ancient Egyptian tomb near the mud-brick pyramid of Lahun shows the site was used 1,000 years earlier than archaeologists previously thought.
The burial site, 130km (80 miles) south of Cairo, was previously dated to Pharaoh Senuseret II - 4,000 years ago.
It became well-known last month when a cache of mummies was found there.
But a chance discovery of a shard of pottery has led to evidence that Lahun was an important site 5,000 years ago - long before the pyramid was built.
Among the subsequent discoveries were an ancient staircase and a coffin.
The wooden box contains the remains of a man who died in his 40s - from the engravings on the item archaeologists say it was most likely a senior figure in the Egyptian government of the second dynasty.
The body is not very well preserved as the tomb predates the era when the Egyptians mummified their dead.
But around it archaeologists have discovered a number of the man's prized possessions, the BBC's Christian Fraser in Cairo says.
There was an offering table, a headrest, two spears and a bed constructed of pine from Lebanon.
The items recovered could help scholars better understand Egyptian carpentry techniques of the time.
This is an exciting period in Egyptology, our correspondent says - archaeologists have uncovered several important tombs this year.
One near the step pyramid of Saqqara protected a perfectly preserved mummy inside and another, discovered last month in Lahun, contained a series of exquisitely painted, brightly coloured sarcophagi which dated from a much earlier period.