Teng Ziying, a farmer from Central China's Hunan Province, and her family have returned a donation paid by the local railway police station and have instead asked for a full explanation.

Teng Ziying and her granddaughter. [Xiaoxiang Morning Post]

Teng, who is in great need of money to treat her granddaughter's leukaemia, said: "I demand an explanation rather than cash," Xinhua reported.

Teng bought a ticket on March 26 from Changsha, the provincial capital, to her hometown Shimen to collect a treatment fee for her three-year-old granddaughter who is in a hospital in the city. However, she boarded the wrong train and transferred to another one the next morning with the same ticket.

During her 10-hour journey home, she picked up 28 empty bottles left in the train's carriages, hoping to sell them. But when she got off the train, she was taken to the local railway police station.

She pleaded with police that she had no idea that collecting empty bottles on trains is prohibited. She claims she was told that "we don't let you know so as to catch you."

After 4 hours of questioning and investigation, Teng was detained, accused of "disturbing order on the train."

Two days later, Teng developed symptoms of illness and was permitted to call her daughter. She was released when her family arrived and paid 400 yuan (US$50) in bail and a 175-yuan (US$20) accommodation fee.

According to the railway police, the regulation stipulates that acts such as gathering rubbish on trains and at stations should be punished.

Thus they are doing their job according to the rule, a leader of the railway police said. He said Teng was turned in to local public security based on a full investigation and evidence and received a punishment of five days' detention. But due to Teng's health, she was kept there less than two days.

Local media reported Teng's story and she became the centre of public attention.

A month later, leaders of the railway police station and local police security paid respective visits to Teng's family and donated a total of 6,000 yuan (US$750) for her granddaughter's treatment.

Teng turned down the donation because public security refused to cancel her case.

It was reported on Friday that the Hunan provincial public security department will carry out further investigation and collect evidence.

Teng's story has now filtered out further afield. Legal experts said her detention obviously lacked full evidence.

Jiang Xueyue, a researcher with Hunan University, noted that Teng's behaviour had not caused social disorder such as the mess of the carriage and the economic loss of the passengers yet she was severely punished for her actions, reported a local Hunan newspaper.

He said regulations are set to secure the basic social order of every citizen rather than undermine people's basic rights.

Yang Zheng, a 32-year old Beijing resident, said the story made her feel sad, as the incident had added to the family's misery. She said she hoped law enforcement authorities would put people first when implementing the law and deal with each case individually.