Queensland Department of Natural Resources and Mines Staff that brought to light the health hazards, suggested people should not use more than once the water bottles, as they are made of polyethylene terephthalate (Pet) containing potential cancer agents.

According to the study, repeated washing and rinsing could make the plastic crack and the carcinogens can leak into drinking water.

A few companies have labels on their bottles warning people of reuse, but nowhere has it been cautioned that 'reuse may cause health hazards'.

"I heard about such a study for the first time from you. We are not sure about the authenticity of the report. If it is true, we will alert our customers," Parvez Hassan, deputy general manager of a Dhaka-based mineral water company, told Star City.

The label on the company's bottles reads "Please crush after use."

"We advertise this warning to prevent other companies from reusing our bottles -- a business gimmick. We did not know the reuse of these bottles could lead to cancer," he said.

Authorities and quality-control departments of mineral water companies believe Pet bottles are safe, as they say there is no chemical reaction between water and polyethylene terephthalate.

"Pet bottles are used around the world and Bangladesh Standard Testing Institution approved them for use here too," said ASM Haider Ali, a bottled-water quality controller.

Some companies produce Pet bottles on their own.

"We import resin (an artificial substance similar to natural resin, used in making plastics) from Japan and Korea to produce the bottles. There is nothing wrong with it," said Hasan Imam, manager of marketing department of a popular mineral water company.

The label on his company's bottles reads: "This water is packed in Pet bottle, which is approved by USA for food packaging." But it has no caution about reuse.

"We cannot print such caution on labels, as we are not aware of further developments," he said of the findings that the bottles are safe for single-use only: if one keeps them longer, it should be no more than a week and the bottles should be kept away from heat.

The Consumers' Association of Bangladesh (CAB) says the country has no law or policy on labels.

"The BSTI is responsible for the quality of water, not bottles or labels," said Emdad Hossain Malek, CAB programme officer.

A health ministry official said authorities took an initiative to draft a national policy on label standards. The committee led by Nurul Amin, additional secretary of the industries ministry, sat once and formed a sub-committee to review the laws and policies of neighbouring countries.

"Policies are necessary to protect our national products. The quality of labels is not up to the mark and information given is not adequate," an official working for a mineral water company said on condition of anonymity.

Most housewives store drinking water in used Pet bottles round the year, unaware of the consequences.

"We used to store water in glass bottles. We now use plastic bottles as they are cheap and available," said Samira Khatun, a Kalabagan resident.

Experts cautioned that children should be protected from the reuse of disposable plastic bottles as it could harm their health.