At least 10 tonnes of toxic tofu were seized by police. Tofu, made from soy milk, is a main ingredient in Chinese cuisine Flickr/FotoosVanRobin

At least 10 tonnes of "toxic" tofu containing banned substances for food production have been seized by Chinese authorities.

The tofu – which is made from soy milk and is a main ingredient in Chinese cuisine - was made with products that can cause cancer, including pure rongalite, a bleaching agent.

The food was produced by a gang in the province of Shandong, eastern China, which used banned products to make the tofu shinier and chewier.

Authorities believed that the seized food is only a small part of the estimated 100 tonnes of tofu that could have been put on the market.

The discovery also led to the arrest of four men.

Authorities believe the factory where they found the toxic food and 190 kilos of rongalite was set up by three cousins.

The episode occurred only a few months after two children died and another 30 fell ill after poisoning at a kindergarten in Yunnan province's rural Qiubei county, south-western China.

Investigators identified the toxic substance as rat poison, which was contained in snacks brought to the kindergarten by a student who shared them with other children.

Last year, 900 people accused of food-forgery crimes including the selling of rat meat and fox as beef and mutton were arrested.

The mass-arrest followed an investigation that unveiled more than 380 cases of meat-related offences and more than 20,000 tonnes of fake food products.