Salt Lake City ? Doctors upgraded the condition of separated conjoined 4-year-old twins Sunday to serious but stable.

Kendra and Maliyah Herrin, who were born fused at the mid-torso, had been in critical condition since their separation in a 26-hour surgery that ended Aug. 8 at Primary Children’s Medical Center. They were removed from ventilators Saturday.

Doctors waited to upgrade the twins’ condition until the girls spent 24 hours breathing on their own, hospital spokeswoman Laura Winder said.

The girls remain on heavy pain medication in the pediatric intensive care unit. Winder said they have opened their eyes, but it’s unclear how aware they are.