In a statement on Sunday evening, prosecutor-general Hamada El-Sawy, who inspected the accident site, said eyewitnesses told the Egyptian public prosecution's team in charge of the investigation that the accident was caused by an electrical short circuit in a power generator.
So far, the public prosecution has questioned 14 of the injured, the statement added.
The prosecution team has examined all of the victims' bodies and found no outward injuries on the deceased bodies except suffocation signs, added the statement.
The death toll stood at 41 and injuries at 14, including two police officers and two personnel, the prosecution said.
The public prosecution also ordered the Public Administration for Criminal Evidence to collect the traces in the scene in order to determine the cause of the accident and how it happened.
The blaze began at 8:57 am at the Giza's church in the Imbaba district during the Divine Liturgy.
All victims have been transferred to Imbaba General Hospital and Al-Agouza Hospital for treatment.
The Egyptian Red Crescent has also dispatched two psychological support teams to the two hospitals where victims of the fire are receiving treatment to help them get over the tragic event.
President Abdel-Fattah El-Sisi, state bodies, and Al-Azhar extend their condolences to the victims' families.
Prime Minister Mostafa Madbouly visited the victims receiving medical treatment in the two hospitals accompanied by Minister of Health Khaled Abdel-Ghaffar, Minister of Social Solidarity Nevine El-Qabbaj, and Minister of Local Development Hisham Amna.
In TV remarks, Madbouly said immediate compensation worth EGP 100,000 will be granted to each of the families of each deceased person, and up to EGP 20,000 will be granted to the families of the injured based on the degree of the injury.
Also, Egypt’s top Islamic authority Al-Azhar and civil society organisations will pay additional compensation of EGP 50,000 to the families of the victims, El-Qabbaj said earlier.