Li was allegedly one of the conspirators behind the escape bid of 12 fugitives, himself included, who were arrested in mainland waters last summer while trying to flee to Taiwan on a speedboat.

Li’s sister wrote on a Facebook page, “Andy is Missing”, and said they received Li's communication.

“Thanks to continued attention, [the authorities] know they cannot just lock him away,” the Facebook page added.

Li, who might be a tainted witness, reportedly stayed at Siu Lam Psychiatric Centre in Tuen Mun under the custody of a “secret group”.

Li was among six people arrested last year for allegedly colluding with foreign forces. Other arrested included media tycoon Jimmy Lai Chee-ying and activist Agnes Chow Ting.

In December, ten of the 12 fugitives received sentences ranging from seven months to three years by a Shenzhen court. Two minors returned to Hong Kong, where they may face further charges.

Other 20 individuals were arrested for allegedly aiding the escape by Hong Kong police.