Authorities said Tuesday morning that a vehicle left running in a garage was the source of carbon monoxide that took the lives of a Lincoln couple on Monday. The deaths are considered accidental.

The victims were identified as 30-year-old Brandon Grueber and his wife, 31-year-old Angela Grueber. Police were called to the 3500 block of North 72nd Street at 2:40 p.m. when a relative discovered the bodies.

The garage is directly below the couple's bedroom and the vehicle was not running when police arrived. Investigators initially said that was not the source of the carbon monoxide, but further investigation revealed that the keys were in the ignition and the ignition was turned on. The car had run out of gas.

This tragedy shows how carbon monoxide can be a silent danger in our homes this time of year. Leaving the car running in the garage for 10 or 15 minutes is all it takes for carbon monoxide to creep into your home and possibly claim lives.

"Carbon monoxide is a by-product that's coming out of the exhaust on a car and it won't take too awful long for it to get you into big trouble and even kill you," says Jim Champion at Charlie Graham Auto in Omaha.

Champion says forgetting about a running vehicle could be easy to do. "If somebody pulls in the garage, they're grabbing groceries, whatever, they open the door, they get groceries, all that stuff they get out of the vehicle, hit the garage door, they accidentally left it running, they go in the house, you're in huge trouble."

Especially considering how quietly engines now run. "They run so quietly anymore that they could be running inside the garage for an extended period of time, you're just not going to know it."

Technology could also play a part. With remote start, a child playing with a keychain could inadvertently start a vehicle in the garage. "So make sure to keep the keys out of everyone's reach and never, ever start it inside the garage even if the door’s open."

The Omaha Fire Department wants to make sure others have lifesaving detectors. "We've had cases in as little as 15 minutes from one that's had a car running in the garage too long or a defective furnace where it's not properly flued and if you have one of these in your house, it will detect that immediately," says OFD Capt. James Gentile.

When rescue crews go on a minor medical call they will check homeowners' detectors to make sure they are working properly. “If they need a smoke detector or a CO detector, we'll offer to put one in for free for 'em,” says Gentile.

Carbon monoxide detectors range from $25-$75 at a hardware store or you can contact the fire department for a free smoke or carbon monoxide detector. Call the Omaha Fire Department at 444-3560 to set up an appointment to have one installed.

It has not been disclosed if the Gruebers had a working carbon monoxide detector in their home.