WFAA-TV

Police said early reports said the victims had high levels of carbon monoxide in their system.

DALLAS — One person died and five others were injured after an apparent carbon monoxide leak.

Sources said the victims were all members of the same family who had come to Dallas from out of town to attend a party with other relatives. The family stayed the night at a house in the 10000 block of Springhaven, which was where the next morning they showed signs of being ill.

"They were having spasms, sick, couldn't move and this sounds like gas poisoning," said Veronica Thompson, a relative of the victims.

A male relative got a call from someone inside the house Sunday afternoon and he called 911 and rushed to the scene after the caller informed him everyone inside the home was sick.

"They had noted they had a high level of carbon monoxide poisoning in their blood system," said Annette Ponce, Dallas Fire-Rescue. "So, the fact they are reporting a high level of carbon monoxide in their system that leads us to believe there was a leak in the home."

An unidentified woman believed to be in her mid-to-late 30s died, while two of her children, ages 13 and 16, are listed in critical condition at Baylor University Medical Center. Three others, including a man who became ill at the scene, were also treated.

Fire officials said the carbon monoxide apparently quickly vented when the doors were opened.

"There were windows open," Ponce said. "The doors were open. So, when they did try to take a reading with the meter that they have on the fire engines, that meter did not read carbon monoxide. It read zero."

Un-vented or improperly vented space heaters and leaking chimneys are often the cause of carbon-monoxide-related poisonings.

Dallas Fire-Rescue officials said they are investigating the incident.

E-mail dronan@wfaa.com