SINGAPORE (AP) -- Singapore has banned three types of China-made toothpaste after tests showed they contained a poisonous chemical that has also raised concerns in other countries.

The city-state tested all toothpaste manufactured in China in response to recent concerns elsewhere that the products may be tainted with diethylene glycol, a Health Sciences Authority statement said Tuesday.

The chemical is a thickening agent used in antifreeze and also as a low-cost, but frequently deadly, substitute for glycerin, commonly used in medicines.

The health authority found that three kinds of toothpaste sold in Singapore - "Hei Mei," "Hei Mei Calcium" and "Maxam" - contained between 0.8 percent and 3.9 percent of the chemical, and ordered the companies to pull the items off the shelves.

"The presence of an undeclared ingredient like (diethylene glycol) raises questions on the quality of these products," the statement said.

It did not say how many tubes were seized, and calls to the agency rang unanswered Wednesday.

The ban by Singapore's health authorities follows reports of contamination in several countries, including Panama, where diethylene glycol was blamed for the deaths of 51 people after they took tainted cold medicine.

China has admitted it was the source of the deadly chemical, but insists it had originally been labeled as being for industrial use only.

Officials in Panama and several other Latin American countries have removed tens of thousands of tubes of Chinese-made toothpaste from stores amid concerns that they contain diethylene glycol. In the U.S., authorities have warned consumers to avoid using toothpaste made in China.

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