HONG KONG — A co-owner of a Hong Kong publishing house who has been held in China for two years has not been heard from, despite assertions by the Chinese authorities that he was released last week, his daughter said Tuesday.

The publisher, Gui Minhai, was a co-owner of Mighty Current Media and its bookshop in the Causeway Bay district of Hong Kong, which sold popular, thinly sourced potboilers about China’s leaders. The mysterious detention of Mr. Gui and four of his colleagues two years ago raised questions about the rule of law in Hong Kong, a semiautonomous Chinese city, and efforts by China to silence critics beyond its borders.

Mr. Gui, a Chinese-born Swedish citizen, disappeared from his home in Thailand on Oct. 17, 2015. He appeared on Chinese state television in January 2016, giving what appeared to be a forced confession to a drunken-driving fatality in China more than a decade earlier. He said he had returned to China voluntarily to face justice, but his supporters said they believed he had been kidnapped as part of an effort to shut down an irritant to China’s ruling Communist Party.

Four other men associated with the publishing house were also detained and were later released. One, Lee Bo, disappeared off the streets of Hong Kong, but denied he had been kidnapped. Another, Lam Wing-kee, spoke out after he was released last year, describing long periods of solitary confinement and a forced confession.