SUGAR doesn't always sweeten the deal as some winemakers in the French Beaujolais region have found out.

They have been accused of illegally adding sugar to fortify their wines or increase volume, reported The Daily Telegraph.

Under suspicion are some 100 growers who are believed to have used 600 tons of sugar to raise alcohol levels above official limits.

They are also suspected of exceeding wine volume quotas and selling the extra bottles on the black market.

The investigation is the latest blow to the region - hit by a recent scandal involving mixing wines and accusations of favouring quantity over quality.

French police arrested five people earlier this month who reportedly admitted to having sold the sugar in northern Beaujolais between 2004 and last year.

The police suspect winemakers of not mentioning the 'invisible' sugar supplies in their carefully monitored records on 'chaptalisation' - adding sugar to unfermented wine musts.

Chaptalisation has been used since the 18th century, but there are strict limits to how much sugar can be added.

Others may have used the sugar to increase volume and feed excess wine into a 'parallel' market to circumvent quotas.

The first discovery in the case was made three years ago, but it may have been taking place as early as 1998. The inquiry could put into question all the 2004 and 2005 vintages of the producers implicated.

Last year, the French wine producer credited with transforming Beaujolais Nouveau into a global phenomenon was found guilty of mixing low-grade wine with top vintages.

'King of Beaujolais' Georges Duboeuf, 72, was convicted of 'fraud and attempted fraud concerning the origin and quality of wines' and fined 20,000 pounds ($58,600).