DALLAS (CBSDFW.COM) – Two children and two adults died from carbon monoxide poisoning Sunday morning in Dallas, firefighters say.

The Dallas Fire-Rescue responded to an emergency carbon monoxide call around 9:30 a.m. at a house on the 1400 block of Owega Avenue.

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The house is under construction. The owner of the house made the call after he found two men and two children dead inside.

The home owner said the two men were working on the house. The workers and the two children who belong to one of them slept in the house overnight.

Both children are under two years of age.

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They were using a generator, which was originally placed outside; however, someone tried to steal it.

In response to the attempted crime, the men brought it inside the house to keep it safe.

Firefighters said it’s unknown how long the generator was inside the house. It was on long enough to reach fatal levels.

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Firefighters said they found the victims in the back bedroom. the generator was found in a separate room.