Trespassing treasure hunters are travelling the length of the country to loot a Carlisle landmark.

Their desperation to unearth rare finds at the site has seen them cause extensive damage to an area already closed while flood recovery work continues.

A stretch of the Hadrian’s Wall Path, running alongside the River Eden at the sprawling Sheepmount sports complex, has become impassible following the appearance of at least six large craters.

The holes are several feet deep and city council chiefs suspect they have been dug by hand using picks and shovels by collectors drawn to the site.

The council, which owns the land, has now been forced to draft in a security firm and is warning the cost is not covered by insurance.

The step was taken after the scale of the problem exploded on the eve of the bank holiday weekend.

Those trying to clamp down on the collectors say one group was seen arriving in a minibus and another was stopped trying to take a mini digger to the area to do their excavations.

Some have come from Plymouth – almost 400 miles away – while others from Durham have been spoken to by council officials.

Gavin Capstick, contracts and community services manager at Carlisle City Council, said: “It is attractive to people who want to unearth and collect items like Victorian bottles, porcelain pots, that kind of thing. They are very collectable. The Victorians used landfill to raise the banks and so people today are effectively taking away a Victorian flood defence that has been doing a job since then.

“But it is breaking and entering and you’re talking about trespass and criminal damage. We’ve had to bring a security firm in and they are reporting incidents to police.”

He added: “I came down here at quarter to eight on Saturday morning and there was already seven of them here.

“There was another three here on Friday afternoon and I know I’ve had to ask four or five groups to leave over the last week or so.”

Efforts to fully reopen the Sheepmount are being hampered by the treasure hunters.

The council says the extent of the damage means it cannot risk opening the site due to fears for public safety.

Huge amounts of earth have been dug out and council chiefs say soil has also been excavated from underneath the parts of the path which remain visible.

The council has come under fire in recent weeks for not getting the Sheepmount’s athletics and other sporting facilities back in action quickly following the winter storms.

Mr Capstick said: “We had reached a point where we could secure this site and get public access back, but now we’re going to have to get contractors in to secure this whole area at considerable expense.”

Councillor Colin Glover, leader of Carlisle City Council, said: “The damage done by the floods is a significant civil engineering job on its own and safety of the site relating to that has been a concern since day one. We’ve now managed to get things like the athletics track back open under supervision, but things like this are significantly slowing down the reopening of the whole site for people who just want to come down here to enjoy it.

“Pursuing their hobby for digging Victorian landfill is now causing real problems for others who want to come here.

“It wasn’t long ago that you could come down here, but this is now going to be a considerable cost to bring the Hadrian’s Wall Path back into use.”

Walkers of the Roman route have been diverted through the city centre since the floods.

It was known that the site was becoming increasingly popular with collectors. Early small scale issues escalated a few days ago, prompting the council to reveal the extent of the problem today (Tuesday).

Mr Glover said: “It had been a problem but we were trying to keep it quiet as so not to encourage people to come down here but it has reached such a point this time that we’re asking people to stay away because it is not safe. It is also dangerous and illegal.”

There are growing concerns treasure hunters will move onto other parts of the route, owned by other authorities.

Work continues to reinstate flood-hit facilities at the Sheepmount while council officers evaluate the best long-term option for sports there.