The suspects -- who were arrested last week after police recovered Leonardo's painting, "Madonna with the Yarnwinder" in Glasgow -- appeared separately at Dumfries Sheriff Court.
Robert Graham, 55, and John Doyle, 58, both of Ormskirk; Calum Jones, 52, of Kilmacolm; and Marshall Ronald, 51, of Skelmersdale made no plea or declaration and were committed for further examination, the BBC has reported.
All four were granted bail with conditions.
So far, nobody has come forward to claim any reward as a result of the recovery of the artwork, the BBC said.
The painting is valued at more than $60 million.