Chinese authorities have seized 64 tonnes of milk powder and products laced with the same deadly toxic additive that sparked an uproar in 2008.

Samples of milk powder found in north-west provinces Gansu and Qinghai had levels of the chemical melamine up to 500 times the permitted limit, the official Xinhua news agency said.

Suspected tainted powder also turned up in the country's north-east.

As well as seizing 38 tonnes of milk powder found with 500 times the limit, police in Qinghai seized 26 tonnes of dairy powder with lower amounts of melamine and 12 tonnes of finished products, a quality watchdog official in Qinghai said.

The man would not give his name and did not specify the products.

The exposure of tainted milk products in poor and remote parts of north-west China has underscored the persistence of food safety problems that have alarmed consumers and sparked criminal scandals that led to executions and official sackings.

Two years ago, at least least six children died and nearly 300,000 children fell ill from drinking powdered milk laced with melamine, an industrial compound added to fool inspectors by giving misleadingly high results in protein tests.

Faced with outrage from consumers, anguished parents and an international outcry, Beijing blamed officials in the northern province Hebei for covering up the problem dairy products.

The products were sold mainly by Hebei's now bankrupt Sanlu Group, which was partly owned by New Zealand dairy giant Fonterra.

China executed two people last November for their role in the scandal.

The latest report did not mention any deaths or illnesses blamed on the latest batches of toxic dairy products.

Melamine can cause kidney stones and is used to make plastics, fertilisers and concrete.

Its high nitrogen content allows protein levels to appear higher when added to milk or animal feed, allowing traders to disguise substandard products.

- Reuters