Egyptian investigators say an internal explosion appears to have caused a Russian passenger jet to crash in the Sinai peninsula on October 31, killing all 224 people aboard -- most of them Russians.
The investigators said on November 4 that they have not determined if the blast was caused by fuel or a bomb.
They have expanded their search area to an area of 40 square kilometers for further evidence.
A Russian investigator said the probe was examing two possibilities -- whether an object stowed on board caused the explosion or a technical fault.
Egyptian investigators also said on November 4 that the cockpit voice recorder of the Metrojet's Airbus A321-200 was partially damaged and that it will take much work to extract its data.
The United Kingdom, meanwhile, has suspended British flights over the Sinai Peninsula after saying the plane may have been brought down by an explosive device.
The developments come two days after U.S. officials said satellite imagery suggested the plane was destroyed by a bomb or a fuel-tank explosion after taking off from the Red Sea resort of Sharm el-Sheikh en route to St. Petersburg.
Militants linked to the Islamic State group have claimed responsibility for downing the plane.
Experts say they were unlikely to have the type of missiles needed to shoot the plane down from the ground.