Beijing's market regulators have launched an official probe into the street vendor known as "goose leg auntie" after she admitted that the popular grilled legs she has sold for years are actually made from duck.

"We are verifying conduct suspected of misleading consumers and will handle the case according to the law," the Haidian district administration for market regulation said on Thursday, adding that authorities have immediately launched an investigation and questioned individuals involved.

The announcement came after Chen Xiufeng, 56, the vendor behind the nickname, confessed in a customer group chat that she had switched from goose legs to duck legs more than a decade ago but kept the name "goose leg auntie." Hashtags related to the incident quickly went viral on Chinese social media on Wednesday, drawing widespread criticism and calls for stronger consumer protection.

Chen rose to fame in late 2023 when students from Peking University, Tsinghua University and Renmin University of China were seen lining up for hours at her stall.

But on Tuesday, Chen posted an announcement in one of her customer group chats saying that the raw material is duck legs.

"I will make it clear in the future. If you mind, please do not place orders. The name ‘goose leg auntie' has been used for over 10 years. There is no fraud involved," she wrote.

The admission came after a customer in Beijing's central business area, Guomao, reported her to authorities. Chen also claimed in the group that she had been "reported by an office elite" and was "cooperating with relevant departments".

Hashtags about the incident quickly topped trending lists on Chinese social media. Many students expressed a sense of betrayal.

Xue Siyuan, a master's student at Renmin University's School of Journalism, said that when he learned the supposed goose leg was actually duck, his first reaction was bewilderment.

He said he would not call himself angry, but rather "a little unsettled".

Xue joined Chen's group-buy chat in May 2022, but did not try the grilled legs until around October that year.

"I always thought I was eating goose legs, because she promoted herself as ‘goose leg auntie' and sold ‘goose legs'," Xue recalled.

"It was really popular — getting a leg was almost impossible. She opened orders at fixed times every day, and you had to grab it the moment it opened," Xue said.

Market data reveal a significant price difference between goose and duck legs. According to wholesale platform 1688.com, frozen duck legs cost only 2 to 3 yuan (30 to 44 cents) each, while goose legs are more expensive, at 6 to 7 yuan each.

As the controversy deepened, consumers came forward with photos showing that some of the roasted legs they had purchased appeared greenish in color. Chen's family responded that the green color came from a "vegetable juice marinade", describing it as their "secret recipe".

Fu Jian, director of Henan Zejin Law Firm, told Dahe News — a newspaper in Henan — that by continuing to use the "goose leg" name to promote sales without informing customers of the ingredient change, Chen violated consumers' right to know and could face claims for triple damages under China's Consumer Rights Protection Law.

The China Consumers Association told China Newsweek, a Beijing-based magazine, on Thursday that it had noticed the incident and would collect leads and report them to relevant government departments.

Chen said she switched from goose legs to duck legs after just one or two months when the supply of goose legs was cut off, but kept the name because longtime customers already knew about the change.

Public records show that between 2024 and 2026, Chen applied for multiple trademarks for the name "goose leg auntie" across various categories, some of which have been successfully registered.