Diogo Jota was on his way to take a ferry and return to Liverpool for pre-season training when he died in a car accident, BBC Sport has been told.
The Portugal forward, who was 28, had undergone minor surgery so doctors had advised him against flying.
As a result, he was planning to return to Liverpool for the start of pre-season, due to begin on Monday, by boat.
This is understood to mean he was travelling by car from Porto to take a ferry from Santander in northern Spain.
There are ferry routes from Santander to Plymouth and Portsmouth in the south of England.