Two adults and two children were overcome by carbon monoxide fumes from a faulty water heater in an apartment in Chillum last night, and four rescue workers who took them to a hospital also showed symptoms of carbon monoxide exposure, Prince George's County officials said.

Seven people were treated and released from Washington Adventist Hospital in Takoma Park, hospital spokesman Robert Jepson said early today. The eighth person, a 65-year-old woman, was transferred to Shady Grove Adventist Hospital in Rockville for treatment in a hyperbaric oxygen chamber, he said.

About 7:15 p.m., Prince George's firefighters responded to a report of three sick people at an apartment in the 5900 block of Eastern Avenue, said Mark Brady, spokesman for Prince George's County Fire/EMS.

Four Montgomery County EMS workers, who were summoned to assist Prince George's firefighters, began examining the 65-year-old woman and two children, ages 5 and 7, and removed them from the building because of suspicions about a carbon monoxide leak, Brady said.

Authorities evacuated the other 11 apartments in the building while they searched for the source.

The four EMS workers who took the woman and two children to the hospital began to feel ill themselves, Brady said. A fourth civilian showed up at the hospital for treatment, hospital officials said. No other residents of the building were treated, and all were permitted to return to their apartments late last night.

Carbon monoxide is an odorless gas that inhibits the body's ability to process oxygen.