"Alcoa has decided to put up for sale its factory in France and two plants in Spain," the director of the plant in the southern French town of Castelsarrasin, Franck Listuzzi, told AFP, confirming a report in a local newspaper.

"The three plants are interlinked and constitute a single system," he added.

The factories in Amorebieta and Alicante in Spain produce material for Castelsarrasin to turn into polished aluminium.

Alcoa said in a statement that "to determine which path to follow and the means to optimise activity at Amorebieta, Alicante and Castelsarrasin, we are exploring several options, including selling the three plants".

The Amorebieta site, near Bilbao, employs 401 staff while 294 work at the Alicante facility. The Castelsarrasin plant has 41 permanent employees and a dozen short-term staff.

Listuzzi said the decision to seek to sell the plants was made due to strategic investment decisions and came as a surprise to staff.

Nevertheless, "Alcoa executives say that if at the end of the process that they don't find a buyer they are committed to continue to operate these sites which are profitable," said Listuzzi.

Alcoa said it was convinced the sites had potential, but given funding constraints it was exploring if they would be more valuable to another owner.