DHAKA (AFP) - Up to 600 workers at a Bangladesh garment factory near the capital fell sick on Wednesday after drinking suspected contaminated water at their workplace, the police and factory sources told Agence France-Presse.

"Primarily we suspect the water supply of the Starlight Sweaters factory was poisoned or contaminated," local industrial police officer Mahfuzur Rahman said.

Many of the workers at the factory in Gazipur were taken to hospital after they started vomiting in the morning, he said.

The factory's administrative officer Based Ali told Agence France-Presse that the number of affected workers could be as high as 600. "The workers have been sent to different hospitals after they reported stomach pain and started vomiting. We estimate the number could be up to 600," he said.

The accident follows the collapse of a building housing five garment factories in April that killed 1,129 people.

The tragedy has led to renewed scrutiny on "made-in-Bangladesh" clothes, which are commonly sold in the West.

The factories in the collapsed nine-storey Rana Plaza just outside Dhaka had made clothing for Western retailers, including Italy's Benetton, Britain's Primark and Spain's Mango.

An official from Bangladesh's Garment Manufacturers and Exporters Association (BGMEA), which represents the country's 4,500 garment plants, said the contamination could have been deliberate.

"We are suspecting that it was poisoning of the water. It could be some sort of pesticide," Mr S.M. Mannan, a vice-president of the BGMEA, told Agence France-Presse.

"This is an A-grade factory. It has its own water supply which comes from a deep tube well, so there is no scope for contamination. Someone might have mixed poison to the water," he added.

Earlier in the day, the police fired rubber bullets and tear gas at a protest by the families of missing garment workers presumed dead in the factory disaster. Officials in the Dhaka suburb of Savar, where the building collapsed on April 24, said a thousand-strong crowd of relatives and garment workers gathered at the site of the wrecked building.

They demanded that the authorities publish a full list of missing workers to allow families to claim compensation.

"There were up to 1,000 protesters, they blocked a key highway and staged a sit-in in front of the ruined site for nearly three hours," said local industrial police inspector Amjad Hossain.

Savar police officer Sheikh Farid Uddin said his officers clashed with the protesters after they failed to move off the highway and began throwing stones.

"In retaliation, we had to fire rubber bullets and tear gas to disperse them," Mr Uddin said.