Authorities in northern Mali say a Swiss woman who was once kidnapped by armed militants in 2012 has been abducted a second time.

Witnesses say her door was found open Friday morning in the northern town of Timbuktu. Footprints in the sand showed where the attackers had apparently scaled the walls of her home.

A Malian intelligence official, who spoke on condition of anonymity as he was not authorized to talk to journalists, said it is not known which group is responsible.

Switzerland's Foreign Ministry says it is aware of a "suspected kidnapping of a female Swiss national in Mali."

Before, she wound up in the hands of extremist group Ansar Dine, who said when she was released that if she came back to Timbuktu they would kill her.