DANYANG, China - Chinese authorities are investigating whether two companies from this coastal region exported tainted toothpaste as more contaminated product, including some made for children, has turned up in Latin America.

A team of government investigators arrived here Sunday afternoon and closed the factory of the Danyang City Success Household Chemical Company, a small building housing about 30 workers in a nearby village, according to villagers and one factory worker. The government also questioned the manager of another toothpaste maker, Goldcredit International Trading, which is in Wuxi, about an hour's drive southeast of here.

No tainted toothpaste has been found in the United States, but a spokesman for the Food and Drug Administration said yesterday that the agency would be taking "a hard look" at whether to issue an import alert.

Authorities in the Dominican Republic said they seized 36,000 tubes of toothpaste suspected of containing diethylene glycol, an industrial solvent and prime ingredient in some antifreeze. Included were tubes of toothpaste marketed for children with bubble gum and strawberry flavors sold under the name of "Mr. Cool Junior."

Toothpaste containing the toxic solvent was also found in Panama and Australia in the last week.

Bautista Rojas Gรณmez, the secretary of health of the Dominican Republic, said the toothpaste, with diethylene glycol listed as an ingredient, was found in stores and warehouses across the country, including near the Haitian border.

Diethylene glycol is the same poison that the Panamanian government unwittingly mixed into cold medicine last year, killing at least 100 people. In that case, the poison falsely labeled as glycerin, a harmless syrup, originated in China, shipping records show. Diethylene glycol is generally less expensive than its chemical cousin glycerin.

Panamanian authorities said they believed the tainted toothpaste found in their country, containing up to 4.6 percent diethylene glycol, came from China.

Executives from both companies under investigation in China denied in interviews on Monday that they had exported any toothpaste containing diethylene glycol to Panama.

"We didn't do this; we didn't make the bad stuff," said Shi Lei, a manager at Danyang City Success. "It was probably someone else."

But Ms. Shi and other toothpaste makers in this region said that diethylene glycol had been used in toothpaste in China for years and that producers believed it was not very harmful.

Government investigators arrived here just days after customs officials in Panama said that they had discovered diethylene glycol in 6,000 tubes of toothpaste. The toothpaste was being sold under the English brand names Mr. Cool and Excel.

There have been no reports of deaths tied to toothpaste containing the chemical.

Dr. Douglas Throckmorton, deputy director for the Center for Drug Evaluation and Research at the F.D.A., said diethylene glycol levels found in some Panamanian toothpaste was nearly 50 times greater than what is deemed safe. "Kids swallow toothpaste," Dr. Throckmorton said. "That is going to be a concern to you."

Suspicion over China's role in the tainted toothpaste and cold medicine comes just weeks after investigators blamed two Chinese companies for intentionally shipping pet food ingredients contaminated with an industrial chemical to the United States, leading to one of the largest pet food recalls in history. The cases are fueling mounting concerns about the quality and safety of China's food and drug exports and threatening to turn into a trade dispute.

After initially rejecting any Chinese role in the tainted pet food, Beijing officials banned the use of melamine, an industrial chemical used in fertilizer and plastics, from vegetable proteins. Melamine and several related chemicals had been discovered in contaminated pet food ingredients. Chinese officials also promised to overhaul its food safety regulations and tighten export controls.

Indeed, the government seems to have responded quickly to reports last weekend about contaminated toothpaste. Hu Keyu, the manager at Goldcredit International, said investigators had talked to him over the weekend because his company was the first to sell and export toothpaste under the brand label Mr. Cool. But he and his staff insisted that Goldcredit never exported to Panama, and that this year the company had exported only a small amount of Mr. Cool toothpaste to Australia. Goldcredit executives said they did not sell toothpaste under the Excel brand name.

Mr. Hu said his company exports toothpaste, toothbrushes, glue and other goods to the United States, Europe and other regions but that his company no longer uses diethylene glycol. He said, however, that most toothpaste makers in this region use diethylene glycol because it is considered a cheap substitute for glycerin.

"You know, if you're in the export market, the margins are small, so people use the substitute," he said. "Even one percent or half a percent price difference can matter to people here."

Executives from Goldcredit and Danyang said the brand Mr. Cool had been copied by several other companies and that numerous trading companies could be exporting the products.

Danyang City Success Household Chemical, however, said that while it did not export to Panama, it has used diethylene glycol in its toothpaste, and that the government does not have a clear regulation on how much can be added. Danyang City Success is a small company in a village in Danyang, a city whose entrance boasts that it has been designated one of China's "national sanitary" cities for its cleanliness.

Danyang City Success produces both Mr. Cool and Excel and exports toothpaste around the world, including to Europe and Africa, company executives said. But this afternoon, villagers and one young factory worker, who declined to give her name, said that investigators had arrived Sunday night and closed the factory to investigate possible contamination in its exports. Ms. Shi, one of the managers along with her husband, met a reporter at the entrance to the factory and insisted her company had nothing to do with the case in Panama. Inside the gate a team of investigators could be seen meeting with company officials and then departing with a bag of documents. Villagers said the investigators were provincial and local officials, including the village's Communist party secretary.

The sister of the party secretary, who only gave her name as Miss Hu, said Danyang City Success had been around for four or five years and that it was run by a former salesman and his wife, Ms. Shi, who grew up in the village.

"He used to sell packaging materials. Then he saved up his money and started this toothpaste company," she said. "But lately the company has been struggling."

Mr. Hu at Goldcredit said that while he did not produce the toothpaste shipped to Panama, diethylene glycol had been used for years at very low levels in Chinese toothpaste as a glycerin substitute. "If diethylene glycol were poisonous," he said, "all Chinese people would have been poisoned."