Brown confirmed during a meeting with reporters prior to the Cavs' game in Boston that Bynum was out for an indefinite period for conduct detrimental to the team. However, he provided no clue into what Bynum had done, the Cleveland Plain Dealer said.
Brown said the situation was "an internal matter," the newspaper said.
The transgression, however, appeared to be the last straw for the Cavs. Sources told ESPN.com Bynum was on the trading bloc and the team was anxious to move him.
A team spokesman told ESPN.com the Cavaliers have canceled a promotional giveaway scheduled for Sunday featuring Bynum.
Cleveland must decide by Jan. 7 to guarantee Bynum's contract for the rest of the season. ESPN.com said $6 million of the $24 million over two seasons, which Bynum signed for last summer, was guaranteed.
Bynum's 7-foot height made him a promising prospect when he entered the NBA. He was part of two NBA championship teams with the Los Angeles Lakers but missed all of last season with a knee injury.
Critics have questioned Bynum's enthusiasm for the grueling NBA game but ESPN said Brown discounted the notion Bynum did not want to continue playing.
Bynum has averaged 20 minutes per game this season as well as 8.4 points and 5.3 rebounds.