Their bus collided with a lorry on a highway, the source said. Seven of those killed were officers.
An initial toll had said the crash killed 15 soldiers but two others died in hospital of their injuries.
The bus had been travelling on the El-Alamein highway when the accident took place. The lorry driver survived the crash.
After the accident, the army sent a plane to transport the victims to a military hospital.
Bad driving and lax enforcement of traffic regulations are often blamed for the high frequency of road accidents in Egypt.