chemical had been exported to Central America, the latest in a series of scandals involving tainted Chinese products. The announcement came the same day a state-run newspaper issued an unusually critical editorial berating the country's food safety regulators for their dithering response to an earlier scandal involving tainted pet food ingredients.
"Our quality watchdogs' contradictory statements regarding responsibility for the sensational pet food scandal was a shameful lack of professionalism," the China Daily said. "They first denied, then soon admitted that the contaminated pet food originated in China."
Pet food ingredients from China tainted with the mildly toxic chemical melamine were blamed in the deaths of dogs and cats in North America earlier this year, prompting a massive pet food recall and, eventually, an investigation in China.
However, the newspaper said that while some exported food didn't meet international standards, the bigger problem was China's domestic food safety situation. It called on the government to do more to protect Chinese consumers.
"It is an open secret here that our manufacturers usually employ higher standards when it comes to exports," it said.
A joint task force involving customs and the State Food and Drug Administration had been formed to investigate the toothpaste contamination reports, the main food safety regulator, the General Administration of Quality Supervision, Inspection and Quarantine, said it in a statement on its Web site.
It said investigators were pursuing leads in both Beijing and the eastern province of Jiangsu.
"The Chinese government has always placed a heavy importance of food and drug safety," the statement said. It said investigators would clarify the situation and apportion responsibility, and would announce their results as soon as they could be obtained.
China's notorious food safety problems have in recent weeks become a matter of international concern, a situation reflected in the agenda for trade talks between Chinese and American officials in Washington this week.
On Tuesday, U.S. Labor Secretary Elaine Chao said Chinese officials told her they would fully investigate any problems discovered in Chinese food exports.
Wednesday's statement didn't say what companies were being checked into, although the general manager of a company based in Jiangsu -- Danyang Chengshi Household Chemical Co. -- said Tuesday he was being questioned by investigators.
Chen Yaozu said he had exported toothpaste containing small amounts of diethylene glycol to Panama -- later shipped to the Dominican Republic -- but said that was permitted under Chinese rules and did not pose a direct health risk. Diethylene glycol is primarily used to keep toothpaste moist.
The chemical, a thickening agent often used as a low-cost substitute for glycerin, was blamed for the deaths of at least 51 people in Panama last year after it was mixed into cough syrup.
Chen's claim echoed those of Chinese chemical companies and makers of animal feed who said adding melamine was safe in controlled amounts. The chemical contains no nutrition but is rich in nitrogen, making the feed appear to have a higher protein content.
Panama also removed the Chinese toothpaste brands from stores last week, but said the level of diethylene glycol did not appear to be dangerous. Still, officials in both countries advised consumers not to use the products.
China's Cabinet earlier this month ordered a thorough crackdown against unsafe practices in the food industry.
