By Yanan Wang

Labour activist Hua Haifeng had avoided legal trouble in his 14 years investigating companies in China, but that changed after he looked into a factory that made shoes for Ivanka Trump's brand.

Hua and two colleagues had worked undercover in factories that manufactured shoes for the brand of US President Donald Trump's daughter and other foreign firms when they were detained in May.

The 36-year-old activist and the two other men, who work for New York-based non-profit China Labor Watch (CLW), were accused of using "spying and other monitoring equipment".

The government has intensified a crackdown on human rights activists and lawyers in recent years.

But Hua told AFP he believes the factory's link to the Ivanka Trump brand may have been a "factor that attracted police interest", though he cannot confirm it.

"As for Ms. Ivanka and her family, I want to say that business activities should abide by business regulations, and not use a family's political resources for personal commercial gain," said Hua.

Hua, who was released on bail in June along with his colleagues, said he was interrogated on 16 occasions for up to three hours at a time. He was kept in a shared cell where he slept beside a urine bucket.

For the first week he was not given access to a lawyer, but the father of two said his conditions gradually improved as his wife paid the authorities to give him better food.

Li Qiang, CLW's founding director, said the case marks the first time activists have faced police trouble in the non-profit's 17-year history.

"But this is the first time we've investigated Ivanka Trump (suppliers), so it may very well be related to the brand," Li said.

'Respect the law'

The activists had been probing two plants owned by major footwear producer Huajian Group -- one in the city of Dongguan in southern Guangdong province, the other in southern Jiangxi province's Ganzhou.

A CLW statement alleged that factory employees worked 15-hour days with minimal breaks and no overtime pay, among other labor abuses.

Collectively, the investigators worked undercover at the factories for several weeks between March and May.

Huajian Group did not respond to repeated requests for comment, but it has previously denied the allegations.

For her part, Ivanka Trump company president Abigail Klem said in a statement: "After discussions with our licensee, we have determined that Ivanka Trump brand products have not been produced at the factory in question since March."

But CLW said they found the Ivanka Trump company listed on Huajian's production schedules for May and June, along with several other prominent overseas fashion brands.

The investigators' arrest put a fresh spotlight on Chinese business activities linked to the US presidential family.

Ivanka Trump, who is a White House advisor, has taken a formal leave of absence from her fashion brand, announcing in January that she is no longer involved with the company's management or day-to-day operations.

Her husband, Jared Kushner, is also a top aide to the US president and his own family business has come under scrutiny over its financial dealings in China.

"I don't know much about (Ivanka Trump's) women's fashion brand, but any company or brand should respect the law and fulfill their responsibility towards society," Hua said.

The activist said the police in their questioning had been focused on a watch equipped with a camera, which was in a suitcase but had never been used.

He said he only took cell phone photos of the public areas surrounding Dongguan.

Hua worked in one factory for a day and was detained before he could go to another one.

World's factory

Hua and his fellow investigators have not been officially charged, nor has a trial date been set.

Authorities said the case was still being investigated and declined to provide additional information.

Hua, back home in central Hubei province, vowed to never stop doing labor rights work.

"China is the world's factory; our workers work for the entire world," he said. "In the decades since economic reform and opening up, the labor community has paid too much."