Three NBA teams have been fined an undisclosed amount for tampering, the league said Monday.

The league said a memo was sent to the NBA's 30 teams announcing the penalties, but with no specific teams or fines mentioned.

The Atlanta Hawks say they were one of the three teams, saying that they "fully understand and respect the NBA's decision."

ESPN.com has also learned that the Houston Rockets were also fined what one source called a "small" amount. The identity of the third team fined was not immediately known.

The memo, according to USA Today, indicated the league fined the three teams because of respective "statements by a team employee to the media, a team email to prospective season ticket purchases, and articles posted online on a team website, each related to players who are currently under contract to other teams but who will become free agents this summer."

The reference to the team email to prospective season-ticket holders likely refers to a recent letter from a Hawks employee that specifically named Los Angeles Lakers center Dwight Howard and Los Angeles Clippers guard Chris Paul as potential Hawks signees.

Sources say that the online articles referenced in the memo were posted on the Rockets' team website.

Information from The Associated Press was used in this report.