Two women and a dog were found dead in a North Dallas apartment Thursday, police say.
According to Dallas Fire-Rescue, shortly before 10 a.m. they were called to perform a welfare check at an apartment on the 17800 block of Vail Street. When the arrived, maintenance workers forced open the locked door and firefighters entered.
Moments later, DFR said firefighters found the bodies of both women and the dog.
The latest news from around North Texas.
Initial field tests were positive for carbon monoxide, DFR said, and they called-in their hazardous materials team to assist in the investigation.
Though the hazardous materials team confirmed the presence of the gas, they were unable to identify an exact source.
According to the Centers for Disease Control and Prevention, carbon monoxide is an odorless and colorless gas that can cause sudden illness and death. The gas is produced any time a fossil fuel is burned and, if it builds up indoors, can be deadly. Carbon monoxide poisoning is often referred to as "the silent killer." Though the dangerous gas cannot be seen, smelled or heard, it can be detected. It is not clear if there was a CO detector in the residence.
The Denton County Medical Examiner will confirm the causes of death.