Two New Yorkers have pleaded guilty to importing from China tens of thousands of tubes of tainted toothpaste, some of which contained microorganisms and a poison used in antifreeze.

It is the first prosecution in this country based on the discovery of tainted Chinese toothpaste in stores in several states last year. The charges were unsealed yesterday in court at the time of the guilty pleas.

A federal prosecutor, Matthew Bassiur, told Judge Brian Cogan of U.S. District Court in Brooklyn that there was no evidence the defendants, Saifoulaye Diallo and Habib Bah, knew the toothpaste they were importing — which was falsely labeled as being manufactured by Colgate — posed a potential health risk.

“Some of the defendants say they brushed their own teeth with the counterfeit Colgate,” Mr. Bassiur said.

In addition to Diallo and Bah, two importing companies, Mabass and Vidtape, pleaded guilty to importing the toothpaste.

Between the various importers, more than a million tubes of the counterfeit Colgate entered the country, according to court documents. The toothpaste ended up for sale largely in 99-cent stores, prosecutors said.

Testing has shown that some of the tubes contained diethylene glycol, which is a sweet-tasting poison found in antifreeze, in lieu of glycerin, which is harmless and used to thicken toothpaste. The poisonous chemical has also been found in toothpaste from China that was being sold under other brand names besides Colgate.

In China, regulators allow for small amounts of diethylene glycol in toothpaste, according to news reports.

There have been no reports that the toothpaste, which is not typically ingested, injured any purchasers.

Two years ago, tainted cough syrup from China that contained diethylene glycol was linked to the deaths of dozens of Panamanians. Tainted Chinese ingredients in pet food led to the death of dogs and cats in this country.

China executed its former chief food and drug regulator last year for accepting bribes. The execution was widely interpreted as a sign of China’s contrition over the export of tainted products.

In court yesterday, Diallo shed some light on how the toothpaste entered the country.

He said he had gone to a trade show in Canton, China, to order shipments of the toothpaste, which was shipped through Port Newark-Elizabeth Marine Terminal in New Jersey.

Few details emerged about the two defendants, who were principals in a company called the Afro Atlantic Corp. Diallo, 51, who lives in the Bronx, said that he had “never went to school,” in response to a question from Judge Cogan about what level of education he had attained. Bah, 47, of Queens, said he had been educated in Ghana and was awaiting approval to become an American citizen at the time of his arrest.

Both men face up to 10 years in prison.

The packaging of the counterfeit toothpaste was mostly indistinguishable from real Colgate, although the wording did contain some spelling and grammatical errors.

Additionally, the toothpaste was identified as being made in South Africa, in an effort to avoid scrutiny from customs officials.

“Something as routine as brushing your teeth should not be dangerous,” an assistant secretary for the Department of Homeland Security, Julie Myers, said in a statement. “Consumers should not have to worry that criminals have tampered with the products they use or ingest.”