A string of burglaries at the homes of star athletes, including Patrick Mahomes, Travis Kelce, Joe Burrow and Luka Doncic, prompted the FBI to warn professional sports leagues about criminal organizations targeting players.

Athletes are particularly vulnerable because their schedules are public information and their homes may contain easily resellable luxury goods like designer handbags, jewelry and watches as well as cash, the FBI said in a Liaison Information Report obtained by ABC News.

The NFL and NBA alerted their athletes after a wave of break-ins, some of which occurred when players were at games or on the road for games, began in September. The most recent occurred Friday when Dallas police were called to the home of Mavericks star Luka Doncic at around 10:30 p.m. Doncic, like other athletes involved, was not at home at the time of the break-in. He is expected to be sidelined at least a month with a calf injury he suffered in a Christmas Day game and has not commented on the matter.

Other athletes who have been victims include Jalen Brown of the Boston Celtics, the Milwaukee Bucks’ Bobby Portis and the Minnesota Timberwolves’ Mike Conley Jr. Portis said “most of my prized possessions” were stolen in the November incident and he offered a $40,000 reward for information leading to the recovery of the items. The Minnesota home of Linval Joseph, the Vikings’ defensive tackle who now plays for the Dallas Cowboys, was burglarized in November.

“While many burglaries occur while homes are unoccupied, some burglaries occur while residents are home,” the FBI report stated.

“In these instances, individuals are encouraged to seek law enforcement help and avoid engaging with criminals, as they may be armed or use violence if confronted.”

Reached by The Washington Post for comment, the FBI replied: “While we cannot confirm or deny the existence of any specific investigations, the FBI monitors potential threats and regularly shares information with our law enforcement partners and the private sector to help protect public safety. As always, we ask members of the public to report anything they consider suspicious to law enforcement.”

The break-ins had prompted the NBA and NFL to previously suggest that players increase security. In a memo acquired by the Associated Press, the NBA recently urged athletes to update alarm systems, place valuables in a safe, use security services during road trips and have dogs as a security measure. The NFL reminded players not to update social media with check-ins and daily activities until the end of the day and urged them not to post information about expensive items. In addition, Commissioner Roger Goodell said recently that the league’s security department has been in touch with the FBI.

The NBA memo cited a previous FBI briefing that linked the burglaries to “transnational South American Theft Groups” that use “advanced techniques and technologies, including surveillance, drones and signal-jamming devices” for quick-hit burglaries. The ring typically focuses on cash and items such as jewelry, watches and luxury bags that can quickly be resold on the black market.

Athletes were encouraged to keep records and photos of valuables, their location as well as using extra security and being less revealing on social media.

“It’s a transnational crime ring,” an unnamed source told NFL.com’s Tom Pelissero in November, “and over the last three weeks, they’ve focused on NBA and NFL players, and it’s all over the country.”

Break-ins at the residences of Mahomes and Kelce occurred on consecutive days in October. “Obviously it’s frustrating. It’s disappointing, but I can’t get into too many of the details because the investigation is ongoing,” Mahomes told reporters in November. “But it’s something you don’t want to happen to anybody but obviously yourself.”

The home of Cincinnati Bengals quarterback Joe Burrow was the target of a break-in in early December while he was in Dallas for a “Monday Night Football” game. “I feel like my privacy has been violated in more ways than one,” Burrow said, “and way more is already out there than I would want out there and that I care to share, so that’s all I got to say about that.”