The damaged glass roof of an Invercargill business after a piece of wood was thrown from the roof onto the inner city glass awning.

Kids are running rampant over roofs in Invercargill's central business district and business owners are scared someone is going to die.

Earlier this year, 17-year-old George Hill was found dead between two buildings in the South Island town of Timaru. He was believed to have been climbing on roofs.

Police are taking action before a tragedy like that occurs - that even means arresting the teens. A 15-year-old boy was arrested and charged with unlawfully entering a property in an incident last month, after climbing on a roof.

John Hawkins/Stuff Invercargill business manager Neville Cook holds the piece of wood thrown from the roof of his inner city business beside a paint-marked access point for teens to climb to the rooftops.

"Over the past few months, police have attended a small number of calls of this nature, and have taken appropriate action in each instance," Police southern area commander inspector Mike Bowman said.

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Neville Cook, manages an inner-city business. He said there was a group of teenagers trespassing on properties, and while they might be doing it for a bit of fun, they were not thinking about anyone else's safety.

"It's only a matter of time before some falls off and is killed. It just takes one group to start it."

Some of the buildings the teens are running across are eight metres high. The block, situated in the centre of Invercargill, incorporates several large buildings with an open-air car park in the middle.

The site is set to be redeveloped and many of the buildings in the block are vacant.

Trespassing on the buildings used to happen sporadically but since late last month and early December the problem has become chaotic.

"We had someone throwing stuff off the roof on to the street below, police were called and the roof had to be cleared," Cook said.

Cook had the roof cleared because he didn't want the teenagers having any ammunition to throw off the buildings to pedestrians below.

Building owners said it was health and safety issue, but they found it hard to find a way to stop the group of teens clambering about.

Thompson Property Group Invercargill manager Steve McVicar, has a building on the outskirts of the central business district, said: "You can't stop people, if they want to get up there they will find a way."

Kelvin Hotel general manager Aaron Mills said he knew people had tried to climb scaffolding currently surrounding the building.

"We can't stop determined people from trying, we called police directly because it's a health and safety issue."

Also of concern is who would be held liable if someone was to fall off a building or through a roof.

University of Otago faculty of law associate professor Barry Allan said the [ACC] scheme would cover anyone injured on premises.

"While there has been some acceptance in England and Australia that a building owner might have a duty of care in negligence, even to trespassers, any claim of that sort is ruled out by the [ACC] scheme."

While building owners had to ensure a workplace was safe for people who were there for lawful purposes, no such duty was owed to someone trespassing on the property, he said.

An ACC media spokesman agreed and said no-one would be held at fault if a person fell from the trespassing because ACC was a no-fault scheme.

"The bottom line is, if kids are running across rooftops, fall through and get hurt, they are covered like everybody else."

New Zealand law did not give people the right to sue for injury, he said.