FILE PHOTO - Spanish King Juan Carlos (L) talks to Spanish Minister of Defence Carme Chacon during celebrations for St. Carmen's day at Naval Military School in Marin, Northwestern Spain, July 16, 2009. REUTERS/Miguel Vidal

MADRID (Reuters) - Spain’s first female defense minister, Carmen Chacon, once a leadership contender for the main opposition Socialist party, died on Sunday at the age of 46.

“Dismayed by the premature departure of Carmen Chacon. Today all Socialists mourn out of pain and helplessness,” the party said on its Twitter page.

The cause of death has not been confirmed, although Spanish news outlets reported that she had been suffering from heart disease.

Chacon, who was from Barcelona, was defense minister from 2008 to 2011 under Prime Minister Jose Luis Rodriguez Zapatero. She was seven months pregnant when she took on the role, which cast her into the media spotlight.

After Zapatero lost Spain’s 2011 national election, Chacon ran to be the head of the Socialist party but narrowly lost.

She was the party’s secretary for international relations between 2014 and 2016 when she resigned.