MADRID, Jan 3 (Reuters) - Billionaire financier George Soros has bought a 3.1 percent stake in FCC, a source familiar with the matter said on Friday, in a further boost for the indebted Spanish builder already backed by Microsoft founder Bill Gates.
The stake - bought from the company's biggest shareholder Esther Koplowitz, whose daughter chairs the company - is partly held via derivative contracts and also through two funds associated with Soros, the source said.
FCC declined to comment.
FCC shares rallied last week on reports of Soros's involvement, which follows Gates's purchase of a 6 percent stake in FCC in October.
The renewed interest in the building group underlines investor optimism for an economic turnaround in Spain, which exited a prolonged recession in the third quarter of 2013.
FCC shares were up 5.4 percent at 17.15 euros ($23.4) at 12.10 GMT.