When mother Julie Keith bought Styrofoam headstones from a local supermarket for Halloween, she found something more terrifying inside - an apparent plea for help from a Chinese forced labourer.

Oregon resident Mrs Keith found the letter in the pack of KMart decorations in October, and human rights experts have said the letter describes conditions which are known to be real in Chinese labour camps.

This individual letter cannot be verified as genuine.

It reads, with some words in the original Chinese: "Sir: If you occasionally buy this product, please kindly resend this letter to the World Human Right Organization.

"Thousands people here who are under the persicution [sic] of the Chinese Communist Party Government will thank and remember you forever."

The letter's author said the Halloween product was made in Masanjia Labor Camp in Shenyang.

julie keith letter

The letter in full, as found by Julie Keith

The China director at Human Rights Watch, Sophie Richardson, told The Oregonian: "We're in no position to confirm the veracity or origin of this.

"I think it is fair to say the conditions described in the letter certainly conform to what we know about conditions in re-education through labor camps."

But Keith told Fox News a Chinese colleague at the Portland Goodwill store where she works said it looked authentic.

“I fully believe it is real,” she said, describing how the headstones where the letter was found inside of were sealed together and the box was closed with tape.

“It had to have come from where they said.”

She also said she had been criticised and insulted online for posting it online, potentially putting the purported "author" in danger.

She told The Oregonian: "If I really don't need it, I won't buy it if it's made in China. This has really made me more aware. I hope it would make a difference."

The US Immigration and Customs Enforcement's Homeland Security Investigations is looking into the note. It is illegal in the US to import products made by convict labor and forced labor.

The letter says many of the forced labourers are imprisoned as practitioners of Falun Gong, a banned Chinese religion.

Falun Gong activists in the US have called for the letter to be investigated, and say the situation described in the letter is similar to punishments their members have experienced.

falun gong

Practitioners of Falun Gong, a religion banned in China

New Tang Dynasty TV, a Falun Gong channel, reported: "Former detainees at Masanjia have corroborated the claims in the letter."

Dai Liguo, formerly Detained Falun Gong Practitioner told the channel: “I was sent to Masanjia in 1999 and persecuted there. They produce handmade crafts for export.

"Most are plastic and are toxic. I was making Christmas decorations, and also knitted sweaters. I had to work from 5 in the morning to 11 at night.”

Another former prisoner, Guo Yujun, said: “Aside from toilet breaks, we had to sit for the whole day, and make those products. There wasn’t a day off, and we weren’t fed properly. In our case, there was no pay for our work.”