Five brands of oolong tea in China, including Unilever-owned Lipton's Tieguanyin variety, have been found to contain excessive levels of potentially harmful rare-earth elements, China's quality watchdog said.

The five tea brands were among 19 oolong products that were found not adhering to regulatory standards in a check on quality, state-run Shanghai Daily reported.

The check targeted 58 oolong products from seven provinces and regions -- Shanghai, Beijing and the provinces of Jiangsu, Zhejiang, Anhui, Fujian and Guangdong -- according to the General Administration of Quality Supervision, Inspection and Quarantine.

Under Chinese law, rare-earth content should be below 2 milligrams per kilogram, but all had higher levels.

The five brands inspected from the Shanghai region were Mingfeng, Jiaranlu, Zhengxiangyuan, Cuiming and Shenxin.

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In addition to excessive rare-earth content, the Zhengxiangyuan tea was found to have poor flavour.

The inspection also found problems with a Tieguanyin variety of oolong produced for Unilever-owned Lipton, which also failed to meet the standards for rare-earth content, officials said.

The administration said rare earth can help raise output and improve flavour, but overuse in the product can be injurious to health, especially to bones.

The Shanghai Bureau of Quality and Technical Supervision remained silent on the issue on Wednesday.

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Last month, it inspected some locally produced teas, but found no rare-earth content or other problems.

Two brands were found to have less net weight than stated on the package, according to inspectors, the daily report said.

Meanwhile, in another check targeting 114 milk powder products, four producers -- Shaanxi Jin Niu Milk, Nongken Xuehua Milk, Baiyue Milk and Dingbian Dairy -- were ordered to improve quality, but none was found to pose a risk to health, said the administration.