Legendary company Gibson Guitars is being investigated by US federal agents for allegedly using illegal rosewood to make its instruments.

Last Tuesday (17 November) the US Fish and Wildlife Service raided Gibson's manufacturing premises in Nashville, Tenn. They seized wood, computers, files and guitars in an attempt to find evidence that Gibson has shipped the illegal wood from Madagascar via Germany, reports the Guardian newspaper.

Rosewood is a key component in the construction of many guitars, but at £3,000 per cubic metre -- over double the price of mahogany -- it doesn't come cheap. It's also an important export for the troubled East African island state of Madagascar, but due to alleged corruption and environmental issues US companies were barred from importing it under the Lacey Act. The act was originally passed in 1900 as a conservation law protecting endangered species.

Gibson is said to be "fully co-operating" with the investigation. "Gibson is a chain of custody certified buyers that purchases wood from legal suppliers who are to follow all standards," a spokesperson for the company said.

Gibson CEO Henry Juszkiewicz sits on the board of the Rainforest Alliance, which lobbies for sustainable forestry.