A still-and-box alarm response was initiated which is standard for a collapse.
Officials say the rear porch collapsed at a first-floor apartment.
One man and two women fell about six feet into an area below.
One person was taken to the hospital in serious to critical condition.
Two others arrived in fair to good condition.
Investigators were working to secure the remainder of the porch structure at the apartment building.
The STNG Wire contributed to this report.