Gallery in a pickle as Hirst's cow and calf spring a leak

Buying a work by Damien Hirst is always going to be a costly exercise. He is, after all, the highest-selling living artist on the planet whose pieces command unprecedented prices. So spare a thought for Oslo's Museum of Modern Art, which was forced to return the artist's installation of a bisected cow and calf for repairs after the tank of formaldehyde they were in sprang a leak.

Just over a year after Hirst's famous shark was found to be suffering from rot, a second pickled piece, the 1995 Turner Prize-winning Mother and Child Divided, had to be sent back to the artist's studio for emergency repairs, The Art Newspaper will report in its October edition. The tank was on display at the Astrup Fearnley Museum of Modern Art in Oslo when the leak was spotted. The work was immediately sent to the artist's studio in London for emergency repairs. It brings into question the longevity of contemporary works of art that are made with unconventional materials. Gunnar Kvaran, the museum's director, said the damage was caused by a flaw in the glass, and some formaldehyde was lost. "Our insurance will probably have to cover the costs of conservation," he added.

Although only one case in the work was found to be damaged in June, all four parts of the installation were sent back to Hirst. The work was the gallery's most popular and will not be returned until next year.

Grete Arbu, head of collections at the museum, said it had been discussing conservation of the work with the artist before the leak was discovered.

"It had been installed permanently in 1997 and it was just getting tired," she said. "The pressure inside the container is enormous. We just noticed a small leak on the floor beneath the glass, and we sent it back within the week.

"Formaldehyde is very dangerous material. The same container will be kept but the layers of glass will be replaced. We could see it needed to be conserved.

"Many of the contemporary artists' works need to be repaired because they work with so many different techniques, so these things can't last a thousand years," she added. The museum is believed to have bought the piece in 1996, for about £135,000 from White Cube Gallery. It has since acquired several other pieces by Hirst. The intricate restoration work is anticipated to be "quite expensive."

A new version of Mother and Child Divided will be lent by Hirst for the Turner Prize retrospective opening next week, which traces past winners in the prize's history. The original was deemed "too fragile to travel" by the Tate, which has used the artwork as a key image in its promotional poster campaign. A spokeswoman for Hirst's company, Science Ltd, confirmed the leak was being repaired.

A statement read: "The 1993 work is undergoing repair as a minor leak has appeared in one of the tank's seams – this is not a major repair job. Damien has made a second version of this piece for the Tate retrospective." Last year, Hirst was to replace the rotting shark in his The Physical Impossibility of Death in the Mind of Someone Living, which was bought by the American collector, Steve Cohen from Charles Saatchi, in a deal brokered by the Gagosian Gallery for a reported £6.5m three years ago. It was found to have deteriorated dramatically since it was unveiled at the Saatchi Gallery in 1992. The chemical solution that surrounded it had become murky and the shark had changed shape.