Diethylene glycol, a poisonous ingredient in some antifreeze, has been found in 6,000 tubes of toothpaste in Panama, and customs officials there said yesterday that the product appeared to have originated in China.

“Our preliminary information is that it came from China, but we don’t know that with certainty yet,” said Daniel Delgado Diamante, Panama’s director of customs. “We are still checking all the possible imports to see if there could be other shipments.”

Some of the toothpaste, which arrived several months ago in the free trade zone next to the Panama Canal, was re-exported to the Dominican Republic in seven shipments, customs officials said. A newspaper in Australia reported yesterday that one brand of the toothpaste had been found on supermarket shelves there and had been recalled.

Diethylene glycol is the same poison that the Panamanian government inadvertently mixed into cold medicine last year, killing at least 100 people. Records show that in that episode the poison, falsely labeled as glycerin, a harmless syrup, also originated in China.