Local governments have been increasing their efforts to combat sales of counterfeit down jackets, with a city in Jiangsu province announcing enforcement measures that include the confiscation of such goods on Monday.

The announcement follows a recent report by China Central Television about how some manufacturers in Nantong have been using feather fibers as stuffing in their products.

This practice significantly reduces production costs, cutting expenses by nearly half. For instance, the cost of producing a down quilt filled with 90 percent down is 800 yuan ($110), while one filled with feather fibers costs only 400 yuan.

On Monday morning, the Nantong Market Supervision and Administration Bureau said in a statement that market supervision authorities and police departments conducted overnight inspections, during which they secured evidence, seized goods and launched investigations against the producers.

"We will continue to inspect all home textile businesses in the city and strictly crack down on illegal practices such as adulteration and counterfeit products to protect consumers' rights," said the statement.

According to CCTV, the addition of feather fibers to down products, or even replacing down with them entirely, has become an "open secret" in the industry.

Due to their similar appearance, consumers find it challenging to distinguish between feather fibers and genuine down in bedding by sight or touch.

As down jackets have gained popularity with the onset of colder weather, several cities have reported counterfeit products, including children's clothing.

In Jiujiang, Jiangxi province, inspectors discovered inexpensive children's "down" jackets filled with a mixture of feather fibers and various inferior materials.

A store employee told CCTV that the counterfeit down material is widespread among local clothing manufacturers, with 200,000 products having been sold this year. Despite passing quality inspections, these products provide subpar insulation.

An anti-counterfeiting expert known as Dongge on social media said common methods of counterfeiting down jackets include mixing in feather fibers, shredded feathers and even dog and pig hair.

Some manufacturers falsely advertise jackets containing 50 percent white duck down as having 90 percent white duck down or even 90 percent white goose down, leading to significant price differences, he said.

"Consumers cannot tell the difference without cutting open the jacket. Thousands of online stores are involved, including some well-known brands," he added.

Earlier this month, police dismantled a counterfeit down jacket operation in Huzhou, Zhejiang province, seizing over 70,000 items falsely advertised as containing down.

Tags on the jackets claimed 70 percent down content, but testing revealed the actual down content was effectively zero, according to local authorities.

On Nov 7, police detained three suspects and confiscated more than 70,000 fake down jackets, with the total value of the seized items exceeding 7 million yuan. An investigation into the case is ongoing.

Liu Boqian in Beijing contributed to this story.

zhaoruinan@chinadaily.com.cn