WASHINGTON (Reuters) - The Federal Communications Commission has opened a new investigation into whether Sinclair Broadcast Group Inc engaged in misrepresentations or a lack of candor in its failed effort to win approval for a $3.9 billion bid to purchase Tribune Media Co.

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In a June 25 letter to Sinclair posted Wednesday on the FCC’s website, the government agency directed Sinclair to answer a series of questions and provide documents by July 9, warning that “failing to respond accurately and completely to this (letter) constitutes a violation of the act and our rules.”

Sinclair did not immediately respond to a Reuters request for comment.

An administrative judge in March dropped a hearing into allegations that Sinclair, the largest U.S. broadcast station owner, may have misled regulators. Judge Jane Halprin added however that the allegations “are extremely serious charges that reasonably warrant a thorough examination.”

Tribune terminated the sale of 42 TV stations in 33 markets to Sinclair, which has 192 stations, in August. A month earlier the FCC referred the deal for a hearing, questioning Sinclair’s candor over the planned sale of some stations and suggesting Sinclair would effectively retain control over them.

The collapse of the deal, which was backed by U.S. President Donald Trump, potentially ended Sinclair’s hopes of building a national conservative-leaning TV powerhouse that might have rivaled Twenty-First Century Fox Inc’s Fox News.

Sinclair in March said it continues “to maintain that we were completely candid, transparent and honest with the FCC during its review of our proposed acquisition of Tribune Media.”

Andrew Schwartzman, a law professor at Georgetown University, said the FCC could have waited to address the issues when Sinclair’s licenses were up for renewal, but said the inquiry was “inevitable” given the FCC’s prior findings.

After the deal collapsed, the FCC’s Enforcement Bureau said it did not oppose dismissal of the hearing proceeding.

Nexstar Media Group Inc said in December it will buy Tribune in a $4.1 billion deal that would make it the largest regional U.S. TV station operator. The deal is still under review by the Justice Department and the FCC.

Democrats accused Sinclair of slanting news coverage in favor of Republicans. Trump last year criticized the Republican-led FCC for not approving the Tribune deal, saying on Twitter it “would have been a great and much needed Conservative voice for and of the People.”

In 2017, the FCC said it was fining Sinclair $13.38 million after it failed to properly disclose that paid programming that aired on local TV stations was sponsored by a cancer institute.

In the latest inquiry, Sinclair could face new fines.

In May, Walt Disney Co said it would sell its interests in 21 regional sports networks and Fox College Sports to Sinclair for $9.6 billion.