DALLAS (CBSDFW.COM) – Two children and two men who were found dead Sunday from possible carbon monoxide poisoning at a south Dallas home have been identified.

The Dallas County Medical Examiner identified the two young ones as one-year-olds Elijah Joaquin Martinez and Josiah Fabian Martinez. The adults were identified as 23-year-old Nestor Fabian Martinez and 32-year-old Wilmer Alexis Maradiga Ordonez.

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On Sunday, firefighters and police responded to a home in south Dallas in the 1400 block of Owega Avenue after the homeowner found the four people dead inside. The owner told firefighters that the home was under construction, and the two men were there to work on it.

Officials said the two men and two children had slept in the house overnight.

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According to Dallas Fire-Rescue, a power generator inside one of the rooms was found to be the source of high levels of carbon monoxide. It is believed that the generator was kept inside the home overnight after someone reportedly tried to steal it.

“It is unclear how long the generator was inside the house, but with no ventilation, it ran long enough to build up to fatal levels,” Jason Evans of Dallas Fire-Rescue said in a news release.

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Firefighters are urging residents to understand the dangers of carbon monoxide as it’s known as the “invisible killer.” It has no color or odor and can be undetectable without some sort of alarm, detector or handheld tool.