(WLUK) — The homes of high-profile professional athletes are being targeted by “organized and skilled criminals” believed to belong to a South American crime syndicate, according to officials.

A memo obtained by NFL.com says the league issued an alert to team security directors and the NFL Players Union after a string of recent home invasions reported by NFL and NBA players.

“It’s legit,” one source familiar with the situation told NFL.com. “It’s a transnational crime ring, and over the last three weeks, they’ve focused on NBA and NFL players, and it’s all over the country.”

Burglars broke into Kansas City Chiefs quarterback Patrick Mahomes’ residence in Belton, Missouri, just after midnight Oct. 6, the Cass County Sheriff’s Office said.

The following day, as the Chiefs hosted the New Orleans Saints for “Monday Night Football” on Oct. 7, tight end Travis Kelce’s mansion in Leawood, Kansas, was burglarized. At least $20,000 in cash was reportedly stolen.

Milwaukee Bucks forward Bobby Portis posted on social media that at least two people broke into his residence in River Hills on Nov. 2 and “many of [his] prized possessions were stolen.”

Portis and the Bucks were playing the Cleveland Cavaliers at the time of the invasion.

NFL.com says the Minnesota home of former Vikings defensive tackle Linval Joseph, who is now with the Dallas Cowboys, was part of a series of burglaries last weekend, and at least one other current NFL player’s home was burglarized in the past week.

Sources have said the FBI is investigating the wave of break-ins as “international organized crime” and according to the NFL’s memo, the burglars are “believed to be tied” to a South American crime ring. However, law enforcement has not confirmed those claims.

Officials say the perpetrators are nonconfrontational and do not burglarize homes while residents are inside, meaning no injuries have been reported.

By tracking team schedules and the social media accounts of players and their families, the burglars wait until they know the homes are empty — often during games — and then gain access.

Items such as cash, jewelry, watches and handbags are often stolen. The perpetrators reportedly focus their attention on master bedrooms and closets.

According to The Associated Press, burglars conduct extensive surveillance on their targets, “including attempted home deliveries and posing as grounds maintenance or joggers in the neighborhood.”

AP says the burglars have entered the residences through side doors, balconies or second-floor windows and tend to target homes in secluded areas.

Police and NFL security urged players to take precautions, like installing security systems, keeping valuables out of plain sight, not posting on social media in real time and avoiding showing off expensive items on social media.