Niu Shiyu writes to thank contributors on Thursday. CHINA DAILY

Police officer Niu Weilong was able to raise the 300,000 yuan ($45,000) needed for his young daughter's medical treatment in just one day.

The heartwarming fundraising frenzy happened after Niu, who works in Artux, Xinjiang Uygur autonomous region, posted an appeal on an online platform this month.

"The donors hail from different ethnic groups in Xinjiang and all parts of China, and some are even living and working overseas," the 42-year-old said. "A simple 'thanks' cannot express my gratitude to these people, who didn't even know me. I wish them good luck all their lives."

In January, Niu's only daughter, Shiyu, was diagnosed with a rare form of lymphoma and needed chemotherapy.

"My girl suffered a lot during the treatments, and I told her to be strong because she's the child of a policeman," Niu said. "But the stronger she is, the more pain I feel in my heart. After all, she's only 7."

He was also worried that Shiyu's medical checkups and primary treatment were quickly wiping out the family's savings.

Niu's wife, Xiao Ping, works at a property management company. Before their daughter fell ill, the couple had already paid for medical treatment for Niu's mother and father, who were diagnosed with cancer in 2008 and 2012. They couldn't find more money for Shiyu's treatment.

At the suggestion of colleagues at the police station in Artux, Niu wrote a letter on behalf of his daughter early on the morning of Feb 20, asking for help, and posted it on crowdsourcing platform Shuidichou, which means water-drop fundraising.

Niu's friends testified for him, as people raising funds online need to prove their cause is authentic. Zhao Wei, Niu's boss, donated 1,000 yuan.

Niu started receiving telephone calls from people in Xinjiang and other provinces and regions of China only a few minutes after the letter was posted. All said they wanted to lend a hand in helping Shiyu fight her disease.

More people got involved in the campaign that day, with many leaving messages on the site. "As a police officer and public servant, you must have helped and served a lot of people at work. Now it's people's turn to help you out," one said.

At 2 pm that day, when Niu arrived at his daughter's ward, his wife told him: "Our daughter will be saved. Only a few minutes before you came, the money people donated online amounted to 300,000 yuan!"

Niu said he believed he received the money so quickly because of people's respect for police officers in Xinjiang. "They recognize police officers' efforts in Xinjiang to protect people of all ethnic groups and maintain a peaceful living environment," he said.

He said he also believed it was payback for his previous good deeds, including working voluntarily at a local organization to help lift people out of poverty.

The funds raised online are allowing Shiyu to receive chemotherapy.

Niu said he will help more people in need to return the goodness his family has seen.