Marion County Fire District Chief Roy Hari said the cause of the fire was under investigation.
The names of those killed have not yet been released, but Hari said it appears to have been a man, a woman and a child.
Other residents of the nine-unit complex jumped out the windows to avoid the rapidly-moving blaze, which had burned down the central stairwell, Hari said.
He said one person had a broken back, and another a broken ankle. Both were taken to a Salem hospital, along with two more people suffering from smoke inhalation, Hari said.
Nothing within the building is salvageable, Hari said. The building itself has an estimated worth of about $800,000.
About 60 firefighters responded to the two-alarm blaze at about 2 a.m., Hari said.
It's not yet clear whether the apartments in the complex were equipped with smoke detectors, Hari said. Some residents have said there were smoke detectors, while others have told authorities that there were not.
