HONG KONG — When the Chinese Ministry of Public Security arrested nearly 200 people at the end of August for “spreading rumors,” one of the most prominent targets was Wang Xiaolu, a reporter for the respected business magazine Caijing.

Mr. Wang was compelled to confess on television before going to trial. Dressed in a green polo shirt and looking downcast, he told viewers of China Central Television, the main state network, that he had gathered information using private sources “through abnormal channels,” then added to this his “own subjective views.” The article in question, Mr. Wang said, was a “sensational” and “irresponsible” report on the stock market.

That the state would take aim at a publication like Caijing came as a surprise to many. The magazine has a strong reputation for hard-hitting investigations and pushing the boundaries of what the government might deem permissible. Yet it has steered clear of prohibited topics like the Falun Gong movement.

“I know how to measure the boundary lines,” Caijing’s founder, Hu Shuli, who resigned in 2009, told The New York Times in 2005. “We go up to the line — and we might even push it. But we never cross it.”