A boy lost consciousness and 13 adults and children were sickened by carbon monoxide poisoning at a Lynnwood apartment complex Thursday.

Lynnwood police said a tenant in the apartments at 168th Street Southwest and 48th Street was having a large family gathering and someone in the apartment was burning barbecue briquettes in the fireplace, but didn't open the damper.

Police said the family didn't realize anything was wrong until a 3-year-old boy lost consciousness at about 9 p.m.

The family then opened the damper, ventilated the apartment and called 911.

Police officers knocked on doors at the Augusta Glen Apartments to make sure neighbors were OK. Medics assessed 14 people from the apartment. Four of the victims, including the boy, were transported to Swedish Medical Center in Edmonds.

The 3-year-old boy was treated for carbon monoxide poisoning with oxygen therapy. Three adults were at the hospital for observation, Lynnwood police said.

Ten other people, ranging in age from 8 to 34, were treated and transported the Providence Colby Campus in Everett for observation.

No one suffered life-threatening injuries.