Rockstar says it's working on a fix for an issue that has resulted in some vehicles disappearing from players' garages.
"We have received some reports about problems with cars and garages, particularly after upgrading and then completing a mission, and are looking into this now," the company says on its support page.
"This issue may occur if you drive another character's personal vehicle," Rockstar adds. "We are looking into a fix to prevent this from occurring in the future. In the meantime, please try to avoid parking a car in a garage, driving one already in a garage, or getting in a default vehicle, when playing as a character other than the one with your upgrades."
Rockstar also notes that vehicles saved in the garage of one safehouse may not show up in the garage of a different one.
In our GTA 5 review, we said Rockstar's latest is "sprawling, thrilling, and beautiful." We concluded by labelling it "the best Grand Theft Auto yet."
Released last Tuesday, GTA 5 has become the UK's fastest selling game ever, moving more copies in its first week than the total launch week sales of all previous series entries combined.
Launch week sales were 2.4 times greater than GTA 4's and bettered the launch week of Call of Duty: Black Ops, the UK's previous record holder, by almost 250,000 copies.