The NFL issued a security alert to teams and the players' union on Thursday following recent burglaries involving the homes of Kansas City Chiefs stars Patrick Mahomes and Travis Kelce.

In a memo obtained by The Associated Press and multiple other media outlets, the league says homes of professional athletes across multiple sports have become "increasingly targeted for burglaries by organized and skilled groups."

The NFL and other professional sports leagues received a briefing from the FBI last Friday, a source told ABC News.

Law enforcement officials noted these groups target the homes on days the athletes have games. Players were told to take precautions and implement home security measures to reduce the risk of being targeted.

Some of the burglary groups have conducted extensive surveillance on targets, including attempted home deliveries and posing as grounds maintenance or joggers in the neighborhood.

Burglars have entered through side doors, via balconies or through second-floor windows. They've targeted homes in secluded areas and focused on master bedrooms and closet areas.

Players were warned to avoid updating any social media with check-ins or daily activities until the end of the day. Posting expensive items on social media is discouraged.

The homes of Mahomes and Kelce were broken into within days of each other last month, law enforcement reports show. The break-ins happened just before and the day of Kansas City's 26-13 home victory over the New Orleans Saints on Oct. 7, where Kelce's superstar girlfriend Taylor Swift watched from the stands. No injuries were reported in either case.

The Associated Press contributed to this report.