An archaeologist has warned that re-erecting Ethiopia's ancient obelisk in the northern city of Axum could endanger the area's many royal tombs.
The obelisks mark the graves of Axum's ancient rulers
A new vast network of burial chambers has been discovered under a car park near the site where the Axum obelisk was to be restored in September.
David Phillipson, who has excavated the area, told the BBC the obelisk would have to be re-erected "carefully".
The final piece of the Axum obelisk was flown home from Italy on Monday.
The 24-metre, 160 ton monument was looted by Italian troops in 1937.
The huge stone obelisks were built to mark the burial sites of members of the aristocracy of the ancient Axum empire.
"The whole area is riddled with underground tombs and chambers," Mr Phillipson from Cambridge University in the UK told the BBC's Focus on Africa programme.
"Any attempt to re-erect the obelisk which has been sent back from Italy will have to be done extremely carefully if one is to avoid either unnecessary damage to other ancient remains or the possibility of subsidence."
Mr Phillipson also said that the 1,700-year-old Axum obelisk had been made to fall down at some point up to 1,000 years ago and that the Italians had found it lying on the ground in three pieces, which they took to Rome.
He said it was not known why, when or by whom the ground around the obelisk had been dug to make it fall down.
Koichiro Matsuura, director-general of the United Nations cultural agency Unesco, said it was likely that some of the newly-discovered tombs in the area were still intact.
"The opening of these new tombs to the public would represent, moreover, an additional asset for the site, which, by boosting cultural tourism, would contribute to the economic development of the country," he said.
"The site is a royal necropolis used by several dynasties before the Christian era," Unesco said, adding that the network stretches far beyond the perimeter of the present World Heritage site.
Richard Pankhurst, from the University of Addis Ababa and one of the prime movers in the campaign for the return of the Axum obelisk, said he would not want the obelisk's re-erection to interfere with archaeological sites.
"But it is unfortunate - we have been waiting 68 years for the obelisk - that these chambers were not discovered before," he said.