dieters and bodybuilders in Scotland are being warned of the dangers of fat-burning pills that have caused three deaths in the UK this year.

Sir Harry Burns, Scotland's chief medical officer, has told doctors to look out for people suffering from reactions to the chemical 2,4-Dinitrophenol, known as DNP.

The alert follows a surge in the number of people taken to hospital after taking products that contain the potentially lethal substance.

DNP is found in slimming pills traded over the internet and are popular with some bodybuilders and those trying to lose weight.

However, experts say the industrial chemical is "extremely dangerous" to health and, depending on the amount consumed, could possibly lead to coma and death.

Consuming lower amounts over longer periods could lead to cataracts and skin lesions and affect the heart, blood and nervous system.

Symptoms of DNP poisoning include fever, dehydration, nausea, vomiting, sweating, headaches, dizziness and rapid or irregular heartbeat.

In a message to doctors, Sir Harry said: "I would like to alert colleagues to a number of recent hospitalisations and deaths reported across the UK relating to the consumption of 2,4-Dinitrophenol (DNP).

"DNP is an industrial chemical that is unfit for human consumption and illegal for use in foodstuffs. Despite the best efforts to remove products from sale, this product is still available and may be used by people trying to dramatically alter their appearance, such as bodybuilders and those attempting to achieve rapid weight loss.

"Products that contain DNP are difficult to identify but include some products labelled as 'fat burners' or 'slimming aids'.

"Reports suggest that products may have descriptors such as 'Yellow Fat Burner' capsules, 'Fat Burning' capsules and 'Pure Caffeine 200mg' tablets. Under no circumstances should these be consumed.

"Health professionals encountering individuals suspected of consuming this substance should inform them of the dangers and advise them to discontinue use immediately."

Medical staff are also being urged to pass on any of the products patients present to them to the Food Standards Agency, which is taking action to crack down on the illegal sale of DNP.

There have been 16 cases of DNP poisoning in the UK this year, with three suspected in Scotland.

In February, fitness fanatic Sarmad Alladin, 18, a student from Surrey who was known as "Mr Muscles", died after taking the pills.

Leeds University medical student Sarah Houston, 23, was found dead in her bedroom in the city last year after secretly taking DNP to lose weight. At the time her father Geoff, a doctor, said none of her friends or family had known she was taking DNP.

DNP is banned for use as a slimming aid but is freely sold on the internet because it can also be used as a pesticide and in dyes.

About 60 people worldwide have died as a result of taking it.

Rod Ainsworth, a director at the FSA, said: 'It's really important people understand how dangerous DNP is.

"We have been working hard to raise awareness of the dangers of DNP and to encourage people to let us know if they are sold products containing this chemical.

"If people are offered DNP they should not take it and should instead contact the FSA or their local authority."