The NBA came down hard on Miami Heat owner Micky Arison on Monday, fining him $500,000, according to league sources, after he used his Twitter account as a sounding board about the lockout last Friday.

The league did not issue an official announcement, but an NBA spokesman confirmed to ESPN.com that Arison had been fined.

The $500,000 fine, first reported by Yahoo! Sports, is five times the amount other owners have previously been fined for public comments about the ongoing labor situation.

According to multiple league sources, commissioner David Stern was lobbied by some of Arison's fellow owners to levy the stiff fine. Arison and several of his peers have been at growing odds as the lockout has deepened -- a rift which spilled over into cyberspace last week.

Arison sent out a series of tweets from his verified account following the latest breakdown in talks between owners and players. Owners and league executives are under a strict mandate not to discuss the lockout and Arison appeared to violate it several times.

The most serious one came when Arison responded to a fan who wrote: "How's it feel to be apart of ruining the best game in the world? NBA owners/players don't give a damn about fans…and guess what? Fans provide all the money you're fighting over…you greedy (expletive) pigs. Arison replied: "You are barking at the wrong owner."

Arison deleted that tweet less than an hour later, but not before it had caught the attention of the league and especially some other owners. Within minutes, sources said, there was outrage spreading across the league and some calling for Arison to be sanctioned.

Arison's statement appeared to confirm the existence of a divide among owners about recent negotiating positions -- which players' union executive director Billy Hunter has been implying publicly for the last several weeks.

There were several other tweets from Arison that also likely drew ire. When another fan asked Arison what he thought about Clippers' owner Donald Sterling, he replied with a simple "lol."

When one of his followers' suggested that competitive balance among "all 32 teams" was an "unrealistic and stupid idea," Arison re-tweeted it with a smiley face. Arison also deleted that tweet, though later tweeted the smile was for saying there are 32 in the NBA when there are only 30.

Measures to guarantee competitive balance among small-market and big-market teams have been some of the most fiercely debated issues in recent talks. Arison is believed to be on the side of the big market teams, which are in the minority.

Recently Arison has taken an expanded involvement in the talks, regularly traveling to New York to sit in on negotiations with players. At times he was the only owner who was not on the league's labor relations committee to come to meetings.

Last month, he referenced a heated exchange between Heat guard Dwyane Wade and Stern during one session by calling it "a friendly chat" on his Twitter account.

It is the third time the league has fined an owner for improper public comments regarding the labor situation.

Last year, Stern fined Wizards owner Ted Leonsis $100,000 for comments about the owners' want for a hard salary cap. And last month, Stern fined Bobcats owner Michael Jordan $100,000 for telling an Australian media outlet the NBA's current business model was "broken."

Brian Windhorst covers the NBA for ESPN.com.