(Reuters) — Scores of garment workers have fallen sick this week at factories in Cambodia, including two that produce clothing for sportswear groups Puma S.E. and Adidas A.G., workers and the companies said Thursday.

A total of 118 employees passed out at work on Thursday at the Shen Zhou and Daqian Textile factories in Phnom Penh, police said, another blow for an industry fraught with disputes but critical to Cambodia's economy.

Garment manufacturing earns Cambodia more than $5 billion a year in revenue and employs some 600,000 people, many of them breadwinners for impoverished families in the countryside.

"It was hot and I began to vomit, I had diarrhea and others had the same problems," said Nguon Sarith, 30, who was hooked up to an intravenous drip at a hospital in the capital.

She said she did not know the cause, but suspected it may have been food poisoning.

Labor rights group Community Legal Education Center said more than 200 workers had fainted this week.

Both Puma and Adidas said they were closely monitoring the situation while investigations were underway, and affected staff had received medical treatment.

Puma said its representatives had met with police and workers and samples of food from the canteen of Shen Zhou had been sent for laboratory analysis to determine whether the cause of the sickness was food poisoning.

Mass faintings are all too familiar in Cambodia, which has become an important manufacturing center for many high street fashion brands.

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Garment makers have often complained of poor ventilation, strong chemicals and use of potent glue for footwear, although official investigations in recent years have been largely inconclusive.

There were more than 1,000 faintings reported in 2011 alone in factories that are mostly owned by Chinese, Taiwanese and South Koreans. Most workers earn less than $100 per month and many volunteer for overtime to boost their income.

The problems do not stop at faintings. The industry has been plagued by unrest in recent months, with long-running disputes over pay mushrooming into nationwide strikes and anti-government protests that have been violently suppressed by security forces.

Some 18 unions plan to hold a week-long strike on April 17 to demand a minimum wage rise to $160 monthly from $100. The last strike was put down by authorities, which on Jan. 3 used live ammunition to disperse crowds, killing five workers.

Working conditions in the Asian clothing industry rose to international prominence last year after the collapse of a factory in Bangladesh killed more than 1,100 people.