MOSCOW — In December, Russia arrested two of its most senior cybersecurity officials on treason charges, prompting speculation that the pair might have tipped off the American authorities about Russian hacking during the 2016 election campaign.

Prosecutors have released no details since, and the case remains shrouded in mystery. But this week an independent Russian television station, Dozhd, reported that the men had been arrested on charges that they helped the United States detain a prominent criminal hacker two years before the election.

The United States Secret Service, which investigates some online financial fraud, detained the hacker, Roman V. Seleznev, the son of a member of the Russian Parliament, during a vacation in the Maldives in 2014.

He was accused of stealing credit card data in the United States that was traded in the digital underground. In April, a court sentenced him to 27 years in prison.