Former New Mexico Gov. Bill Richardson, a longtime fixture of Democratic politics with turns as Energy Secretary and United Nations ambassador under the Clinton administration, died on Friday, the Richardson Center for Global Engagement said in a statement. He was 75.

Richardson died in his sleep at his summer home in Massachusetts.

"He lived his entire life in the service of others -- including both his time in government and his subsequent career helping to free people held hostage or wrongfully detained abroad. There was no person that Governor Richardson would not speak with if it held the promise of returning a person to freedom," Mickey Bergman, vice president of the Richardson Center, said in a statement.

"The world has lost a champion for those held unjustly abroad and I have lost a mentor and a dear friend."

This is a breaking story and will be updated.