ST. PAUL (AP) - St. Paul fire officials have determined a duplex fire was intentionally set.

St. Paul Fire Marshal Steven Zaccard says the fire Monday night destroyed the duplex. No injuries were reported.

He says bystanders rescued a woman in her 20s and a 7-month-old baby from the burning home. The front of the building was completely engulfed in flames when police and fire crews arrived.

Zaccard says a criminal investigation is underway. He declined to say why investigators believe the cause is arson.

A St. Paul police commander says the woman is not a suspect.

The American Red Cross is assisting one adult and five children who lived in the duplex.