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Chinese authorities said they were investigating the death of Dr. Li Wenliang, who died from the coronavirus early Friday and had been warned by police for raising concerns in the early stages of the outbreak.

The Central Commission for Discipline Inspection, the Chinese Communist Party's internal discipline body, said in a statement it would send a team to Wuhan, "to conduct a comprehensive investigation on the issues reported by the public involving Dr. Li Wenliang."

Li, an eye specialist at the Wuhan Central Hospital, who according to a police document was 33, died at 2:58 a.m. Friday (1:58 ET Thursday), the Wuhan Municipal Health Commission confirmed in a statement, while offering its condolences and "deep sympathy to his family."

The city of Wuhan is the center of the outbreak, which has killed at least 638 people globally and infected more than 31,000 people in mainland China.

Dr. Li Wenliang.

Li had posted pictures of himself in the hospital online, as well as a picture of his diagnosis and the police warning he was given.

The "Letter of Reprimand," dated Jan. 3, accused him of posting "untruthful speech about 7 cases of SARS being diagnosed [relating to ] the Hunan Fruit and Seafood Market" on a WeChat group Dec. 30. The posts were made on a group called "Wuhan University Clinical Class of 04."

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Li warned his fellow university graduates in the group there had been seven confirmed cases and urged them to be cautious, he said on Weibo.

"Your action greatly disturbed public order," the warning said. "Your action has already exceeded the scope of what is permitted by law... It is an unlawful act!"

"We hope you will cool down and reflect carefully, and solemnly warn you," the letter read. "If you stubbornly insist on maintaining your own view without a thought of repentance... you will suffer legal sanctions! Have you got that?"

The letter noted Li's response: "I've got it."

Medical staff wearing protective gear prepare to provide care for suspected coronavirus patients on board the quarantined Diamond Princess cruise ship in Yokohama on Friday. Kazuhiro Nogi / AFP - Getty Images

Li has since become a hero in China and was the subject of more than 2 million posts on Weibo, the Twitter-like social network used across the country, with many praising his commitment. Some criticized the government and called for an apology to his family.

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He had written on Weibo: "I will be on the front line when I get better, and the epidemic is still spreading. I don't want to be a deserter."

The People's Daily, the official newspaper, said in an editorial: "This doctor’s optimism and tenacity are moving."

Many Chinese left tributes on Weibo, including one who wrote: "A great life, a glorious death!" Another said: "Heroes always come from ordinary people. Hope all angels in white can return safely."

China's ambassador to the United States, Cui Tiankai, said in a tweet that he was "saddened" by Li's death.

An incredible outpouring in #China for Dr. Li Wenliang, the brave doctor who had warned of a strange #coronavirus in #Wuhan, only to be censured for ‘spreading rumors’. He died this morning after contracting the virus; he was 34. This sketch everywhere on social media. @NBCNews pic.twitter.com/EQMxvWMkvf — Janis Mackey Frayer (@janisfrayer) February 7, 2020

Global Times, a frequent defender of the regime, reported Friday that Li was "one of eight 'whistleblowers' who tried to warn other medics of the coronavirus outbreak but were reprimanded by local police."

In what was an extremely rare comment on domestic affairs for a Chinese diplomat, during a daily briefing Friday, foreign ministry spokesperson Hua Chunying expressed “condolences” and “sincere sympathy to the bereaved families.”