The Tempe Fire Department said a running generator inside a unit at a Tempe condominium complex is to blame for six cases of carbon monoxide poisoning.

Fire firefighters were called to the complex on Rural Road north of Southern Avenue at about 11 p.m. Wednesday.

The woman who made the call said her carbon monoxide (CO) detector went off and reported feeling sick.

According to Larry Randall, a senior fire inspector with the Tempe Fire Department, firefighters found out that a generator had been running inside one of the units for several hours.

Randall said hazardous-material technicians took readings in several units and found high levels of carbon monoxide in 10 of them.

Firefighters ventilated the homes, checking them again before letting residents back in.

A total of six people were treated at the scene. Three of them, women ages 20, 25 and 46, were taken to Scottsdale Memorial Hospital Osborn.

The others, two young men, 18 and 19, and a 21-year-old woman, were treated and released at the scene.

The fire department said the generator was being used by a restoration contractor to run 10 fans and two dehumidifiers to dry out carpeting that was soaked when a pipe broke.

Carbon monoxide is a poisonous, colorless, odorless, tasteless gas that, according to the National Safety Council, kills between 200 and 300 people each year. 

Symptoms of carbon monoxide poisoning include headaches, dizziness, light-headedness and nausea.

All of the victims in this case are expected to recover.

The incident is under investigation.