Deng Guilian, Hua's wife, told AFP her husband had planned to return to their home for a holiday earlier this week.
Hua Haifeng was working undercover for the US-based China Labor Watch (CLW), which said he had witnessed examples of forced overtime and wage violations.
"The government is taking a harsher line towards activists, especially those working for overseas organizations", said William Nee, China researcher at Amnesty International.
"We appeal to President Trump, Ivanka Trump herself, and to her related brand company to advocate and press for the release our activists", China Labor Watch said in the email to Reuters. "The only reason we think this case is different is that this is Ivanka Trump's factory", he told the Washington Post. Late a year ago, CLW found a slew of labor violations at four factories that appear to produce toys for Mattel, Hasbro, Disney, McDonald's and Wal-Mart.
China Labor Watch has carried out frequent investigations into labor violations in Chinese factories making anything from Disney toys to Apple iPhones. In the past, the worst thing Li feared was having investigators kicked out of a factory or facing a short police detention.
The reported arrest and disappearances come at a time of sustained pressure on labor activists in China amid a crackdown on civil society under President Xi Jinping.
Arrests Hua Haifeng and Li Zhao
China Labor Watch said it had written a letter to Ivanka Trump detailing the allegations in late April but had yet to receive a reply.
There has been no comment so far from Chinese authorities, the Trump administration or the Ivanka Trump brand. This is the first time.
CLW also added that two more activists involved in the investigations are now missing. Li added that a friend had tried to file a missing person report on Li Zhao in Jiangxi, where the factory is located, but was told he had to do so in the man's hometown.
AP was unable to reach the other investigators' families. The parent company is known as Huajian Group. But she said she had received a phone call from the Public Security Bureau in Ganzhou on Monday saying he had been detained on suspicion of "illegal monitoring".
The Huajian Group produces footwear sold by Ivanka Trump's brand, as well as Coach, Karl Lagerfeld, and Kendall + Kylie. Nine West did not respond to requests for comment. While he has no hard proof of this, he says that he has investigated hundreds of factories in China and that while his staff have often been caught and kicked out, they have never been arrested until now.
Li said on separate occasions this month and in April, Hua and one of the other activists, Li Zhao, had attempted to meet him in Hong Kong but were turned away because they were "suspected of criminal activity". "Jiangxi police are just looking for an excuse", he said. Next month, it was expecting to publish a report accusing the company of excessive overtime, low pay as well as possible student intern misuse. Rights groups and journalists have documented widespread abuse of the system over the years. "He is the sole breadwinner in our family and I have two children aged 7 and 3". She said she did not know their current whereabouts.
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