The aircraft was flying with a "standard armament configuration," according to the official who could not provide details on the contents of the package due to operational security commitments. The armament had been secured and was disposed of in accordance with Air Force policies and regulations this afternoon, officials said.
AIR7 HD captured the detonation at Ben Clark Public Safety Training Center in Riverside.
WATCH: Ordnance on F-16 jet detonated in Riverside
Not long after the explosion, the 215 Freeway was reopened in both directions between the Cactus Avenue and Harley Knox Boulevard exits. It was closed for about 24 hours while the military dealt with the ordnance.
F-16 crash impacting Riverside County community
The pilot, who was the only occupant of the aircraft and has not been identified, was ejected before the crash Thursday and safely landed at the airfield near Cactus Avenue and Meridian Parkway where a parachute was spotted. He was said to be in "good" condition.
Officials say the pilot did declare an emergency before ejecting, but won't confirm a possible cause.
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At an afternoon press conference, Michael Messisca of the Riverside University Health System said 13 adult patients were received after the incident. Three were "trauma activation patients." Those three were admitted to the hospital with non-life-threatening injuries and are currently stable. The other 10 were treated for fume and debris exposure and discharged in good condition, some of them were first responders, officials said.
At an earlier press conference, U.S. Air Force officials provided very few details, only saying that clean-up efforts and the investigation are ongoing. The Air Force's Explosive Ordnance Team was on scene at the crash site.
Firefighters responded to the wreck at about 3:40 p.m. Thursday. The aircraft crashed at the end of the runway and into a warehouse, where the building's sprinkler system was set off. A CAL FIRE chief said despite initial reports, a small fire did not ignite.
No fatalities were reported.
Witnesses say the F-16 fighter jet was flying in tandem with another aircraft at low altitude when something went wrong.
Images from AIR7 HD showed a large hole on the roof of the building. Capt. Fernando Herrera with Cal Fire and the Riverside County Fire Department said the first fire unit to arrive confirmed the military aircraft crashed into the tilt-up building.
Authorities conducted a search and the people inside the building were evacuated.
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Fire officials and other agencies created an evacuation zone of about 4,000 feet from the area of impact. Most of the evacuation orders around the crash have since been lifted, however the buildings nearest to the crash are still off limits until the fighter jet is moved.
A photo from inside the building appears to show part of the plane sticking out of the rubble. Jeff Schoffstall said he was working when he heard the plane come dangerously low to the ground before it made a loud noise. He posted video from inside the building.
VIDEO: F-16 goes down moments before it crashes into building near March Air Reserve Base
Another employee talked about witnessing the aftermath of the crash.
"It was almost to the point where I had to cover my ears, and next thing you know I just hear this explosion," said witness Daniel Gallegos. "I turn around to the back of the building and I just seen a burst of flames and just the ceiling start falling through every part of the building. In a matter of seconds, my ankles were filled with water."
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In a brief statement, officials said the pilot was conducting a training mission for North American Aerospace Defense Command, or NORAD.
The pilot is part of the 144th Fighter Wing, an Air National Guard unit based in Fresno.
The aircraft belongs to the South Dakota Air National Guard in Sioux Falls. The United States Air Force Reserve said in a press release that the plane was conducting a training mission for NORAD at the time.
An investigation into the cause of the crash is ongoing.