Sources told Bloomberg that the development raises questions about whether a takeover will happen. Sources told Reuters, however, that the two companies remain in "advanced negotiations" about a potential acquisition.
Shares of Tronc, formerly known as Tribune Publishing, were initially halted around 2:55 p.m ET but resumed trading around 3:01 p.m. ET. The stock was halted again at 3:21 p.m. ET for volatility and reopened around 3:26 p.m. ET.
Shares of Tronc plunged as much as 30 percent and ended the day at $12.27, more than 27 percent lower. Gannett shares plunged 17 percent.
Gannett declined to comment to CNBC. Tronc did not immediately respond to CNBC's request for comment.
Bloomberg previously reported that the two were nearing agreement on the deal, in which Gannett would acquire Tronc for $18.50 to $19 a share.
Previously, USA Today-owner Gannett has made two offers for Tronc, which owns the Los Angeles Times and Chicago Tribune. In April, Gannett made a bid to acquire Tronc for $12.25 per share in cash, an offer that was unanimously rejected by Tronc's board. Gannett subsequently upped its all-cash bid to $15 per share in May. Tronc's board rejected the revised proposal, saying it was "not in the best interests of Tribune shareholders."