Dallas, TX- Authorities said five children were treated for carbon monoxide poisoning after the gas had been leaking into a Dallas apartment Thursday.

Dallas Fire-Rescue officials said they were dispatched to The Hamptons at Lake West in the 2400 block of Bickers Street at 6:20 p.m. after a woman called about her children complaining of not feeling well.

When firefighters arrived, they moved everyone outside as the children were exhibiting signs of a carbon monoxide exposure.

Firefighters said they found traces of carbon monoxide in the apartment, so they called in a hazmat team to investigate.

A hazmat team checked the apartment and found the hot water heater’s ventilation had blocked by pieces of sheet rock, causing the gas to vent into the apartment.

The five children — all between the ages of 1 and 14 years old — were taken to a hospital for evaluation.

No further details have been released.