The maker of a Chinese toothpaste found to contain a potentially deadly chemical said Tuesday that he is under investigation, but claimed his product was safe.

Chen Yaozu, general manager of Danyang Chengshi Household Chemical Co., said Tuesday his firm had exported toothpaste to Panama containing diethylene glycol, a chemical blamed for the deaths of at least 51 people in the Central American country after it was mixed into cough syrup.

Chen said the chemical, a thickening agent often used as a low-cost substitute for glycerin, was permitted under Chinese rules and was safe in small amounts.

"I can say I am very confident about our product's quality," Chen said in a telephone interview from his company's headquarters in the eastern province of Jiangsu. He said company managers were cooperating with investigators.

The safety of Chinese food and pharmaceutical exports has come into question in recent months amid allegations that tainted ingredients from local suppliers ended up in products blamed for the deaths in Panama and for killing pets in North America.

That has put export markets worth about $30 billion on alert, prompting the authorities to take swift action to root out wayward firms and protect its industries.

On Monday, U.S. Secretary of Health and Human Services Michael Leavitt said those problems had been raised at the "highest levels" of China's government, adding he believed China understood the economic risks involved.

"We both know that the world market will disadvantage suppliers that can't provide an assurance of safety," Leavitt said in Washington while hosting a visit by Chinese Health Minister Gao Qiang.

There have been no cases of toothpaste made in China containing diethylene glycol found in the U.S. market.

Chinese Foreign Ministry spokeswoman Jiang Yu responded on Tuesday that Beijing has worked to boost food security and the monitoring of exports.

"We stand ready to work with the international community and explore international cooperation in food security," Jiang said at a regularly scheduled news conference.

An official with the Danyang local branch of China's food and drug inspection agency confirmed the investigation into the toothpaste suppliers, but gave no details. The official gave only his surname, Gu, as is common with Chinese bureaucrats.

Chinese-made toothpaste sold under the brands "Excel" and "Mr. Cool" were targeted after authorities in the Dominican Republic learned they contained diethylene glycol. The toothpaste was imported from Panama and entered the Dominican Republic illegally in shipments registered as food for animals, the Dominican Health Department said.

Panama also removed the toothpaste brands from stores last week, but said the level of diethylene glycol do not appear to be dangerous. Still, officials in both countries have advised consumers not to use the products.

Panama removed the toothpastes after a customer noticed their labels said they contained diethylene glycol. Tests by experts at the University of Panama confirmed the toothpastes contained about a 2.5 percent level of the chemical.

Checks on supermarkets in China's commercial center of Shanghai turned up no sign of diethylene glycol among the listed ingredients of more than one dozen brands of Chinese-made toothpaste.

A salesman for a Chinese trading company that imports the chemical from Iran said it is occasionally be used to prevent toothpaste from drying out.

"Proper amounts of diethylene glycol are not toxic if it remains uncontaminated," said Zou Jianjun of the Jiangsu-based Donghua International Trading Co.

It was unclear if China limits use of the chemical in toothpaste.

The head of another toothpaste maker, Jiangsu Goldcredit International Trading Co., denied a New York Times report published Tuesday that his company was also under investigation or that it had anything to do with toothpaste exported to Panama.

General Manager Hu Keyu said Goldcredit had tried to register the name "Mr. Cool" several years ago, but had not received the trademark. He said Chinese companies had flooded Panama with shoddy drugs and other products and tracing the true source of the toothpaste could be difficult.

"Since profit margins for exported toothpaste are so low, such companies try to use cheaper replacements and that is permitted," Hu said. "If the product came from China, it might have come from anywhere."