China's anti-corruption watchdog says it is investigating Meng Hongwei, who heads the global law enforcement organisation Interpol, for suspected violations of the law.
Mr Meng, 64, who is also Vice-Minister of Public Security in China, had been reported missing after travelling from France, where Interpol is based, to China.
"Public Security Ministry Vice-Minister Meng Hongwei is currently under investigation by the National Supervisory Commission for suspected violations of law," the Chinese anti-corruption body said in a brief statement on its website.
The statement did not specify the nature of the alleged legal violations, and was the first from China since Mr Meng's disappearance was reported in France on Friday.
When asked about the Chinese announcement, France's Interior Ministry said it had no information.
Interpol, which is based in the French city of Lyon, said it had made a formal request to China for information about Mr Meng.
Wife says Mr Meng sent knife emoji as danger signal
Mr Meng's wife Grace, who remains in France, has been placed under police protection after receiving threats.
She told reporters in Lyon that she had not heard from her husband since September 25. Ms Meng said he used his Interpol phone to send her an emoji image of a knife that day, four minutes after he sent a message saying "Wait for my call"/
She said the call never came and she does not know what happened to him.
Of the knife image, she said: "I think he means he is in danger."
She said he was in China when he sent the image.
"This is the last, last message from my husband," she said. "After that I have no call and he disappeared."
Ms Meng detailed the last messages she exchanged with her husband to reporters as part of an impassioned plea to help bring her missing husband to safety.
"I have gone from sorrow and fear to the pursuit of truth, justice and responsibility toward history," she said, her voice trembling with emotion.
"For the husband whom I deeply love, for my young children, for the people of my motherland, for all the wives and children, so that their husbands and fathers will no longer disappear."
Ms Meng would not allow reporters to show her face, saying she feared for her own safety and the safety of her children.
She was accompanied to the hotel where she held her press conference by two French police officers who were assigned to look after her.
Before her husband shared the knife image, she sent him a photo of two animal figurines, one of a bear and another of a horse, meant to represent their two children.
One of them loves horses, she said, and the other "looks like the bear".
She said they had been in daily contact during his trip before he went missing in China.
In his role as a senior public security official in China, Mr Meng regularly travelled between Beijing and Lyon.
He had been on a three-country tour to Norway, Sweden and Serbia for Interpol before his latest trip back to China, Ms Meng said.
Mr Meng 'resigns' as Interpol president
The announcement that Mr Meng was under investigation makes him the latest high-profile official to fall victim to a sweeping crackdown by the ruling Communist Party.
The one-sentence announcement, issued when it was nearly midnight in China, said only that Mr Meng was in the custody of party investigators.
Soon after the statement was released, Interpol announced that Mr Meng had resigned as president, effective immediately.
It did not say why, or provide details about Mr Meng's whereabouts or condition.
Mr Meng was the first person from China to serve as Interpol's president, a post that is largely symbolic but powerful in status.
Interpol's secretary-general is responsible for the day-to-day running of the agency's operations, so Mr Meng's absence is likely to have had little operational effect.
The organisation links up police officials from its 192 member states, who can use Interpol to disseminate their search for a fugitive or a missing person.
Only at the behest of a country does the information go public via a "red notice", the closest thing to an international arrest warrant. "Yellow notices" are issued for missing persons.
Mr Meng has held various positions within China's security establishment, and has been Public Security Ministry Vice-Minister since 2004.
His appointment as Interpol president in 2016 alarmed some human rights organisations, fearful it would embolden China to strike out at dissidents and refugees abroad.
His term as Interpol president was originally due to run until 2020.
Xi Xinping's harsh crackdown on civil society
Mr Meng's unexplained disappearance threatens to tarnish Beijing's image as a rising Asian power.
President Xi Jinping, China's most powerful leader since Mao Zedong, has overseen a harsh crackdown on civil society that is aimed at crushing dissent and activism among lawyers and rights advocates.
He has also used a popular and wide-ranging anti-corruption campaign to boost supervision of the party and as a powerful weapon with which to purge his political opponents.
Mr Meng's various jobs put him in close contact with Chinese leaders in the security establishment, a sector long synonymous with corruption, opacity and human rights abuses.
A member of the Communist Party, Mr Meng worked with former security chief and Politburo Standing Committee member Zhou Yongkang, who is now serving a life sentence for corruption.
However, Ms Meng sought to distance her husband from Mr Zhou, saying the two men did not get on.
She said Mr Zhou had sought to muscle her husband out of the public security ministry — the national police force — several times and disliked her husband "very much".
She did not explain what, if any, relation that animosity may now have with her husband's case.