Philadelphia, PA – Several homes have been evacuated after high levels of carbon monoxide was detected in South Philadelphia Saturday.

Crews were called out to the 700 block of South Hutchinson Street just after 4:30 a.m. where they found two people unresponsive inside a home with high carbon monoxide readings.

Firefighters evacuated four neighboring homes with high readings, and medics transported four people including two firefighters to the Hospital of the University of Pennsylvania for treatment.

Officials believe the problem may have come from a heater in the basement of 723 South Hutchinson Street. Firefighters reported a reading of 150 parts per million inside the home.

The evacuation was lifted within two hours.

PGW crews were called to second location in the Lawncrest section of Philadelphia where carbon monoxide was reported around 6:30 a.m.

Firefighters detected elevated levels of CO at a home in the 600 block of Alcott Street.

Four people were transported to Einstein Hospital. There is no word on their conditions.

Officials believe a faulty heater was also to blame.

Both incidents remain under investigation.

We have attached a chart used to determine the level of carbon monoxide danger below.

Firefighters encourage everyone to have a CO detector in their home.