An ongoing investigation has confirmed that some of a domestic liquor brand's products contain excessive levels of a plasticizer, but there is no evidence that the company has intentionally used the toxic additive, a Chinese local quality watchdog said Wednesday.

In response to the latest food safety scandal, the Hunan provincial administration of quality and technological supervision said the investigation results show that liquor samples from Jiugui Liquor Co., Ltd. contained 1.04 mg of dibutyl phthalate (DBP) per kg, one kind of plasticizer.

The figure is higher than the 0.3 mg per kg standard, a provisional regulatory limit set by the Ministry of Health (MOH) in June 2011 after it found bis (2-ethylhexyl) phthalate (DEHP) in food products from Taiwan the same year.

The inspection is being carried out by the quality watchdog of the Tujia-Miao Autonomous Prefecture of Xiangxi.

It carried out a "law enforcement inspection" at the company, which is based in Jishou City, the prefectural seat of Xiangxi, on Tuesday.

The investigation was launched after a report was released on Monday on www.21cbh.com. The business news website, based in south China's Guangdong Province, said tests conducted by the Shanghai branch of Intertek, a global company, showed that one kind of Jiugui liquor contained 1.08 mg of DBP per kg.

The level was 260 percent higher than the allowed maximum level of 0.3 mg per kg in food as outlined in a document issued by MOH last June, the news article said.

It said four bottles of a type of Jiugui liquor, which sell for 438 yuan (about 70 U.S. dollars) each, were tested.

In a statement posted on its website on Wednesday, the provincial quality watchdog said there is no evidence that the plasticizer was intentionally added to the liquor.

The provincial administration submitted the investigation results to the central quality watchdog, the General Administration of Quality, Inspection and Quarantine.

It also urged the company to determine the sources of the plasticizer and carry out a thorough overhaul of its products.

The provincial administration said it would continue with its investigation and severely deal with any illegal acts.

A major liquor company in Hunan, Jiugui Liquor defended itself on Monday night, saying it did not add the plasticizer in its production process and was checking the tests, according to the news article on www.21cbh.com.

Jiugui Liquor shares on the Shenzhen exchange market have been suspended since Monday, and the news report also caused a sharp drop in the share prices of many other major domestic liquor producers on Monday.

Jiugui liquor products had been taken off some supermarket shelves by Wednesday.

According to experts, plasticizers are used to thicken liquids, but alcohol products do not need this. The chemicals can cause male reproductive issues as well as damage the digestive and immune systems.

Liu Xuejun, a food science professor at Jilin Agricultural University, told Xinhua there was little possibility of intentionally adding plasticizers to alcohol products.

Liu mentioned two possible causes of excessive levels of plasticizers in liquor products. The chemicals may leak from PVC tubes or vessels used for storage or transportation, or they may come from flavoring essences used in liquor.

The China Alcoholic Drinks Association said on Monday large-scale tests on China's liquor products show that almost all alcohol products contain plasticizers, with an average level of 0.537 mg/kg. High-end liquor products contain more plasticizers than low-end ones.

Domestic levels of plasticizers in liquor products were below overseas standards, it said.

The association said the alcohol industry was discussing the limits for allowed levels of plasticizers in liquors.

A wider probe into the country's distilled spirits market has found trace amounts of DEHP, mainly DBP, in some other domestic liquor products, according to Xinhua's interview on Wednesday with officials from AQSIQ, MOH, and the China National Center for Food Safety Risk Assessment.

The probe also found that samples of some imported distilled spirits contained a minute amount of DEHP, AQSIQ officials said.

But no domestic liquor brand covered by the probe has been found to deliberately add plasticizers to their products, the official confirmed.

The taint mainly came from plastic containers, pipes, sealing materials and packages used during production, storage and transport, as well as the environment, the official said, citing analysis given by industry experts.

As distilled spirits must be clear and transparent, there is no need for producers to add DEHP, which is used for thickening and emulsification, the official said.

MOH has blacklisted DEHP, high doses of which can lead to testicular or kidney damage and fertility problems, as an inedible material that is likely to be illegally added to food last year.

DEHP, though banned from being directly added to food products in China, can be widely detected in the environment due to its common use in plastic products, the MOH official said.

Currently, neither the Codex Alimentarius Commission nor any country has set a limit standard on the amount of DEHP found in spirits, the official said.

But estimates made by the China National Center for Food Safety Risk Assessment show that consuming 0.5 kg of the defective Jiugui Liquor products each day will not have an effect on health, the official said.

The AQSIQ official said the government has ordered local quality authorities to expand checks to spirit makers nationwide.

Producers have also been urged to determine the cause of the problem and take necessary measures, such as improving processing equipment and changing packing materials, to correct it, the official said.

The scandal of plasticizers in food was first exposed in Taiwan. In May 2011, the island's health authorities detected toxic plasticizers in food additives used in the production of soft drinks, tea drinks and dietary supplements. Nearly 1,000 products and 300 companies were involved.

Some experts said the toxicity of plasticizers was much more serious than melamine, a chemical raw material which can lead to reproductive damage or bladder or kidney stones.

A 2008 scandal in which milk was laced with melamine led to the deaths of at least six babies and sickened 300,000 others in the Chinese mainland.