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DENVER - Peter Boyles, a well-known and sometimes-controversial radio host in Denver for 630 KHOW, will be off the air Friday after a heated physical exchange with one of his producers, multiple sources connected to the station confirm to 9NEWS.

Employees observed red marks on producer Greg Hollenback's neck within the minutes of the argument, which happened during Thursday morning's broadcast of the Peter Boyles Show.

The sources wished to remain anonymous because they were not authorized to speak on the matter.

"Everyone here is disappointed and devastated," one employee told 9NEWS.

Reached for comment Thursday morning, Boyles told 9NEWS only that he "had a very heated exchange" with Hollenback.

Boyles and Hollenback have worked together for about two decades.

A source inside KHOW tells 9NEWS the incident has been elevated to the corporate level.KHOW management declined to comment, saying the incident is a "personnel matter."

Although he will be off the air Friday, managers would not say whether Boyles was suspended.

Boyles tells 9NEWS libertarian activist Jon Caldara will fill in for him.

It's unclear exactly what led to the exchange. There are no police records of the incident at this time.

9NEWS was at the radio station Thursday morning for Tom Tancredo's announcement of his gubernatorial run in 2014.

ClearChannel issued the following statement Thursday afternoon: "This is a personnel matter. Out of respect for our employees, we are not commenting at this time."