Several restaurants in Shanghai, including McDonald's and Taoyuan Village, said on Tuesday that their products are completely safe after a recent official spot check found 10 eateries selling substandard youtiao, fried dough sticks usually eaten for breakfast.

Officials from the Shanghai Consumer Council raided 29 popular eateries and reported those not changing the cooking oil frequently or producing food of which the amount of certain indicators exceeding the standards to the city's Food and Drug Administration.

Five were closed by the FDA for not having a business license, while another five were ordered to come up to code.

The five that were ordered to make a change and are still in business are two Xinya Dabao branches on Changyang Road and Xingguo Road as well as eateries at No 456 Xiaomuqiao Road, No 500 Anlong Road and No 777 Siping Road.

Youtiao sold in two McDonald's outlets in Yangpu district and a diner in Changning district were found to contain residues of plasticizer, but none exceeded the national upper limit of 1.5 milligrams per kilogram.

"We have verified that no plasticizer is added during the production of the fried dough sticks and their packaging sold at all McDonald's restaurants, and consumers can rest assured," McDonald's China said in a statement.

"The origin of the plasticizer is being thoroughly investigated," the statement continued.

Residual amounts of aluminum of 9.73 milligrams per kg were found in products in a Taoyuan Village outlet in Jing'an district. The restaurant said there was no alum added to its youtiao.

The national standard sets an upper limit of 100 milligrams of aluminum per kg in food products. Excessive intake of the substance can impair the nervous and reproductive systems.

"The residue may come from the natural aluminum content of water or flour. We will provide the public with accurate information about the source of the substance in the food after a thorough investigation," the restaurant said in a statement.

One store in Pudong New Area was selling products containing nearly 10 times the allowed level of aluminum residue.

Tests also showed youtiao from a KFC outlet in Yangpu district contained the highest levels of saturated fatty acid - the excessive intake of which can lead to cardiovascular disease and obesity. The average amount of saturated fatty acid contained in samples taken from the 29 restaurants was 3.5 grams, but the KFC product contained 6.8 grams.

In addition, branches of Yonghe King were inspected.