The five men were all locked in disputes with their onetime employer, the Chinese technology giant Huawei. And they had all joined a group on the social app WeChat to organize.

Then, one of them wrote a message to the group that would upend their lives:

“I can prove that Huawei sold to Iran.”

The message, and the brief discussion that followed, touched on an explosive issue for the company. Huawei had just begun fighting allegations by the U.S. government that it had committed fraud to bypass sanctions against Iran. The company’s chief financial officer, a daughter of its founder, had been arrested less than two weeks earlier as part of the case.

The employees’ messages in the chat group included no hard evidence that Huawei’s activities in Iran were unlawful. Yet within weeks, the Chinese police had arrested all five men, two of them told The New York Times.

The two former employees — Li Hongyuan, 42, and Zeng Meng, 39 — said officers had questioned them about Iran and asked why they had been in contact with foreign news outlets, both topics they had discussed on WeChat.