Liverpool have confirmed an "ongoing situation involving the family of Luis Diaz" amid reports that their striker's parents were kidnapped in Colombia.
Colombia's president said Diaz's mother "has been rescued" but his father remains missing.
Liverpool said they were supporting the player as he sat out the Reds' Premier League clash with Nottingham Forest on Sunday.
"Liverpool Football Club can confirm it is aware of an ongoing situation involving the family of Luis Diaz in Colombia," read a club statement.
"It is our fervent hope that the matter is resolved safely and at the earliest possible opportunity. In the meantime, the player's welfare will continue to be our immediate priority."
Liverpool manager Jurgen Klopp told the BBC: "We had to obviously make a late change because of the private situation involving Luis Diaz.
"It's a worrying situation for all of us and it was a pretty tough night. I have never had that before. It's a new experience I never needed."
Colombia president Gustavo Petro said on X, formerly known as Twitter: "In an operation in Barrancas, Luis Diaz's mother has been rescued, we continue the search for the father."
The country's football federation said in a statement that the kidnapping was regrettable and urged authorities to rescue Diaz's father.
Liverpool signed Diaz from Porto in January 2022 in an initial Stg 37.5 million ($A71.8 million) deal that included a potential extra £12.5 million ($A23.9 million) in add-ons.
The 26-year-old winger has made 11 appearances this season and scored three goals.
Diaz was an unused substitute for Thursday's 5-1 Europa League win against Toulouse after starting the Premier League victory over Everton last weekend.