"The logical explanation is that an explosion brought it down," the official told The Associated Press.
The official, who is part of the Egyptian team investigating the crash that killed all 66 people on board the flight from Paris to Cairo early last Thursday, has personally examined the remains at a Cairo morgue. He spoke on condition of anonymity because he was not authorized to release the information.
However, the head of the government's forensic agency later Tuesday dismissed as speculation all media reports about human remains from the crash indicating an explosion.
"Whatever has been published is baseless and mere assumptions," Hisham Abdel-Hamid told Egypt's state MENA news agency.
A statement from the government's investigative committee also warned media outlets to be cautious about what is published "to avoid chaos and spreading false rumors and damaging the state's high interests and national security."
The Egyptian expert told the AP that all 80 pieces that have been brought to Cairo so far are very small. "There isn't even a whole body part, like an arm or a head," said the official, adding that one piece was the left part of a head.
He said the body parts are "so tiny" and that at least one piece of a human arm has signs of burns - an indication it might have "belonged to a passenger sitting next to the explosion."
"But I cannot say what caused the blast," he said. He did not say whether traces of explosives were found on the human remains retrieved so far.
The expert's comments mark a new dramatic twist surrounding last week's crash, which still remains a mystery. The plane's black boxes have yet to be found and photographs of retrieved debris published by the Egyptian military over the weekend were not charred and appear to show no signs of fire.
Egyptian officials have said they believe terrorism is a more likely explanation than equipment failure, or some other catastrophic event, and some aviation experts have said the erratic flight reported by the Greek defense minister suggests a bomb blast or a struggle in the cockpit.
But so far no hard evidence has emerged on the cause of the disaster.
Also Tuesday, the investigative team led by Ayman al-Moqadem issued its second report on the case, saying that so far pieces of the plane wreckage have been taken to Cairo in 18 batches. It added that the priority is to locate the black boxes and to retrieve more bodies.
France's aviation accident investigation agency would not comment on anything involving the bodies or say whether any information has surfaced in the investigation to indicate an explosion.
A French patrol boat took one doctor on board to help with searches when and if the body parts are found. But the French Navy said that if it finds debris and body parts, this would be first reported to Egyptian authorities and French justice officials.
In a search for clues, family members of the victims gave been arriving during the day Tuesday at the Cairo morgue forensics' department to give DNA samples to help identify the remains of their kin, a security official said. The official also spoke on condition of anonymity because he was not authorized to talk to reporters.
Also, a technical team from Egypt's forensic medicine department went to a hotel near the Cairo International Airport where relatives of the victims are gathered to take DNA samples to use in identifying the bodies.
The EgyptAir crash shocked a nation struggling to revive its ailing economy and contain a resilient insurgency by Islamic militants.
Safety onboard Egyptian aircraft and at the country's airports have been under close international scrutiny since a Russian airliner crashed in the Sinai Peninsula last October, killing all 224 people on board, shortly after taking off from an Egyptian resort. The crash - claimed by the Islamic State affiliate in Sinai and blamed by Moscow on an explosive device planted on board - decimated Egypt's lucrative tourism industry, which had already been battered by years of turmoil in the country.
If mechanical or structural failure is found to be behind the crash of Flight 804, that would deal another severe blow to both tourism and the national carrier. If downed by an act of terror, the Egyptians can point to security at Charles de Gaulle Airport in Paris, from which the plane took off.
Egypt has dispatched a submarine to search for the flight's black boxes and a French ship joined the international effort to locate the wreckage and search for the plane's data recorders.
Ships and planes from Britain, Cyprus, France, Greece and the United States are also taking part in the search for the debris from the aircraft, including the black boxes.
Associated Press writers Angela Charlton and Sylvie Corbet in Paris contributed to this report.