OMAHA, Neb. -- Lincoln Police Tuesday said it appeared a couple died accidently from carbon monoxide poisoning in their home.

Angela and Brandon Grueber were found by relatives Monday afternoon inside a home with high levels of carbon monoxide.

Both were in their early 30's.

Lincoln police said the keys were in the ignition of the couple's vehicle, and it appeared the car had been left running. It was out of gas when fire investigators arrived Monday.

Investigators say there were no signs of a disturbance in the Grueber's Lincoln home, and no sign the deaths were anything but an accident.

The Grueber's were found in their bedroom, directly above the garage

"We will miss Angie's beautiful smile, her sense of humor and her tenacious adherence to doing the right thing for the people we support," said Carla Sorensen, Angela's supervisor and friend at Collaborative Services, where Angela worked with developmentally disabled clients.

Sorensen said Angela was a remarkable young woman who was extremely close to her husband, Brandon.

Firefighters said high levels of carbon monoxide prevented them from entering the home initially. They were able to save a family dog at the scene. Autopsies will determine how the Grueber's died.