Police were called to the Big Horn Apartments in Idaho Springs Sunday morning because a woman there was unresponsive, said Idaho Springs Police.

Christina Santana Mendez, 28, died of an unknown cause at the time of this writing inside her apartment, authorities said.

CBI has been called in to assist PD and will help determine if anything criminal led to her death.

An autopsy is scheduled for later in the week.

This is a developing story. Stay with 9NEWS for updates.