According to SpaceX CEO Elon Musk, the Cape Canaveral mishap was not an explosion but a "fast fire."
On Thursday, a SpaceX Falcon 9 rocket blew up on the launch pad, shaking nearby buildings and spewing smoke into the sky, two days before its planned liftoff with an Israeli satellite.
In his Thursday tweet, Musk did not call the incident an explosion.
Generally, the difference between what might be a "fast fire" and an explosion is the speed of combustion, said Daniel M. Nosenchuck, an associate professor in Princeton University's Mechanical & Aerospace Engineering Department.
While he couldn't comment directly on the SpaceX incident, as he is out of the country and has not followed it closely, he told CNBC Friday that one observable difference between a fire and an explosion is the sound that witnesses hear. The sound of a deflagration, Elon's "fast fire," is different from that of a detonation wave.
A deflagration wave is subsonic, or slower than the speed of sound, whereas a detonation wave is supersonic, faster than the speed of sound.
"So, a 'fast fire' might be a relatively slowly moving deflagration wave, which might produce a 'whooshing' sound. An explosion, which produces the detonation wave, would be characterized by an extremely loud bang as the supersonic combustion front moved past an observer," explained Nosenchuck, who has taught classes on heat transfer.
He also noted that "the pressure rise that occurs behind an explosive detonation wave is nearly instantaneous and can be very large and cause much more structural damage than a deflagration event."
In its latest update on the "anomaly," SpaceX pledged to carefully and thoroughly investigate the event.
Late Friday, the company provided an update on Thursday's events:
SpaceX emphasized that its "number one priority is to safely and reliably return to flight for [its] customers, as well as to take all the necessary steps to ensure the highest possible levels of safety for future crewed missions with the Falcon 9."
— CNBC's Robert Ferris contributed to this report.