President Abdel Fattah al-Sisi offered condolences for those on board, amounting to Egypt's official acknowledgement of their deaths, although there was still no explanation of why the Airbus had crashed.
"The Egyptian navy was able to retrieve more debris from the plane, some of the passengers' belongings, human remains, and plane seats," the Civil Aviation Ministry said in a statement.
The navy was searching an area about 290 km (180 miles) north of the port city of Alexandria, just south of where the signal from the plane was lost early on Thursday.
There was no sign of the bulk of the wreckage, or of a location signal from the "black box" flight recorders.
EgyptAir Chairman Safwat Moslem told state television that the current radius of the search zone was 40 miles (64 km), giving an area of 5,000 sq miles (13,000 sq km), but that it would be expanded as necessary.
A European satellite spotted a 2 km-long oil slick in the Mediterranean, about 40 km southeast of the aircraft's last known position, the European Space Agency said.
Egyptian Prime Minister Sherif Ismail said that it was too early to rule out any cause for the crash. The aviation minister said a terrorist attack was more likely than a technical failure.
Although suspicion pointed to Islamist militants who blew up another airliner over Egypt seven months ago, no group had claimed responsibility more than 36 hours after the disappearance of flight MS804, an Airbus A320 flying from Paris to Cairo.
Jihadists have been fighting Egypt's government since Sisi toppled an elected Islamist leader in 2013. In October, the Islamic State group claimed responsibility for blowing up a Russian airliner that exploded after taking off from an Egyptian tourist resort. Russian investigators blamed a bomb smuggled on board.
That crash devastated Egypt's tourist industry, one of the main sources of foreign exchange for a country of 80 million people, and another similar attack would crush hopes of it recovering.
Three French investigators and a technical expert from Airbus arrived in Cairo early on Friday, airport sources said.
Officials from a number of U.S. agencies told Reuters that a U.S. review of satellite imagery so far had not produced any signs of an explosion. They said the United States had not ruled out any possible causes for the crash, including mechanical failure, terrorism or a deliberate act by the pilot or crew.
The plane vanished just as it was moving from Greek to Egyptian airspace control. Greek Defence Minister Panos Kammenos said it had swerved radically and plunged from 37,000 feet to 15,000 before vanishing from Greek radar screens.
Ultra-hardline Islamists have targeted airports, airliners and tourist sites in Europe, Egypt, Tunisia and other Middle Eastern countries over the past few years.
Khaled al-Gameel, head of crew at EgyptAir, said the pilot, Mahamed Saeed Ali Shouqair, had 15 years' experience and was in charge of training and mentoring younger pilots.
"He comes from a pilot family; his uncle was a high-ranking pilot at EgyptAir and his cousin is also a pilot," Gameel said. "He was very popular and was known for taking it upon himself to settle disputes any two colleagues were having."
A Facebook page that appeared to be Shouqair's showed no signs of Islamist sympathies. It included criticism of the Muslim Brotherhood, repostings of articles supporting President Sisi and pictures of Shouqair wearing aviator sunglasses.
The aircraft was carrying 56 passengers, including one child and two infants, and 10 crew. They included 30 Egyptian and 15 French nationals, along with citizens of 10 other countries. The plane had made scheduled flights to Tunisia and Eritrea on Wednesday before arriving in Paris from Cairo.