AN underground air raid shelter from the Second World War has been unearthed at a key section of the city's tram project sparking fears it may hold the project up further.
Transport officials, however, have insisted it is too early to determine whether the surprise discovery at Haymarket will delay the multi-million-pound scheme.
A spokesman for project manager TIE said: "This may have an impact, but that does not
mean there will be delays. It is too early to say."
The shelter was discovered on Monday evening at Clifton Terrace by workers who thought it was a disused communications box, bricked up many years ago.
When they removed the bricks, the full extent of the shelter became apparent.
It is estimated to be around 15ft deep, housing a series of doors and steps, but workers were told not to venture any further owing to the unknown safety risks.
A worker, wishing to remain anonymous, said: "Everyone was just questioning what it was. We had no idea it was there."
The area is now being made safe before a decision is made by the city council over the future of the structure and whether it could be filled in to allow the project to move on.
This is not the first discovery made by workers digging up the Capital's streets to lay tracks for the controversial tram project.
In March, three mysterious underground, dome-shaped chambers were discovered on Princes Street, thought to date back to the 18th century, made of stone and brick.
The discovery was made close to a bus stop next to the Mound as staff attempted to relocated an underground water pipe.
Medieval human remains were also discovered earlier this month on Constitution Street and TIE's new chief executive Richard Jeffrey confirmed yesterday that an intact coffin, thought to be around 300 years old was also found on Friday in Leith.
Speaking about the air raid shelter, he said: "We have a team of professionals working in design and construction and when we understand the scale of the challenges it poses, we will sit down and work out how to solve it.
"In terms of what it might cost, contractors always envisage that there will be unforeseen issues on any projects and it's only fair that the price is paid for dealing with those issues."
A city council spokeswoman confirmed the discovery and said investigations were under way.
The full article contains 412 words and appears in Edinburgh Evening News newspaper.
