A model has died of suspected malnutrition just months after the death of her elder sister prompted an international debate on underweight "size zero" models.

Eliana Ramos, 18, who worked for a prestigious Argentine modelling agency, was found dead in her bedroom. Six months ago her sister Luisel suffered a fatal heart attack during a catwalk show, having reportedly eaten nothing but lettuce leaves for three months.

Eliana is also said to have had a heart attack, and local media in Uruguay, south America, linked her death to anorexia. A source involved in the investigation into the teenager's death said: "The primary diagnosis is death due to symptoms of malnutrition."

Eliana, known as Elle, was found dead on Tuesday morning by her grandmother at the house they shared in the Uruguayan capital of Montevideo.

She had joined the fashion industry aged 16 and was due to model in the same show at which her 22-year-old sister collapsed on leaving the catwalk at the Hotel Radisson Victoria Plaza in Montevideo last August.

Judge Roberto Timbal has ordered an autopsy. Local police said the cause of Eliana's death was not yet clear.

But Pancho Dotto, founder of the Dotto modelling agency where she worked, insisted that she did not have an eating disorder. He said: "She ate well, she was very healthy and she played sport. It is absurd that people are speaking about anorexia or bulimia in this case.

"She was always a very good and humble girl. She never had problems with her diet. I knew her very well. She was living with us for a while in the summer and she always ate very well. It is obvious the sisters' deaths are due to a genetic problem, and not their diet."

Asked if his agency carried out health checks on their models, Mr Dotto said: "Nowhere in the world do they do medical checks on models, that is absurd."

The death of Luisel Ramos was followed in November by the death from anorexia of a Brazilian model who lived on apples and tomatoes. Ana Carolina Reston, 21, who had worked for Giorgio Armani, weighed just six stone when she died on the eve of an international photoshoot.

The models' deaths sparked an international debate about the ethics of using models who have "size zero" measurements - a 31.5in bust, a 23in waist and 34in hips. The average waist size of a British eight-year-old is 22in.

Five women were recently barred from the catwalk at Madrid's fashion week for being "excessively skinny". The British Fashion Council, the organiser of London Fashion Week which began on Sunday, refused to ban size zero models but wrote to designers asking them only to use healthy-looking girls.

This week the cross-party trade and industry select committee announced that it is considering whether to investigate the "social responsibility" of the fashion industry. Peter Luff, chairman of the committee, said Ms Ramos's death showed once more the seriousness of the issue.

"It is a wake-up call to the fashion industry - but how many wake-up calls does it need to have before it recognises the seriousness of the situation it faces? There is clearly the need for further decisive action."

The British Fashion Council said: "We don't think it is particularly helpful that the media is speculating on this."