Egyptian officials investigating the Metrojet crash have revealed a noise was heard in the last second of the black box recording.
However, the head of the air accident investigation has said this is not enough to satisfy him that an in-flight explosion took place over the Sinai peninsula last Saturday.
"A spectral analysis will be carried out by specialised labs in order to identify the nature of this noise," Ayman el Mokadem added.
The investigator appeared to call on Britain to provide its intelligence into what caused the disaster, as his committee "was not provided with any information" to suggest the plane was brought down deliberately.
Mr el Mokadem told a news conference that the plane's debris was spread over a "wide area" more than 13km in length, which is consistent with an in-flight breakup of the plane.
"Some parts of the wreckage are missing, and it is hoped to locate them in the coming days. The initial observation of the aircraft wreckage does not allow for identifying the origin of the in-flight breakup," he added.
During the conference, one official suggested a passenger's lithium batteries or an explosion in the fuel compartment might be responsible - and warned nothing could be excluded.
Preliminary analysis of data successfully downloaded from the flight recorders suggests the plane was airborne for 23 minutes and 14 seconds.
The last recorded altitude of the Airbus A321 was 30,888ft - and the aircraft was still in climbing mode at the end of the recording, with auto-pilot engaged throughout the flight.
The speed of the plane was 281 knots (323mph)
Mr el Mokadem's confirmation that a noise can be heard at the end of the cockpit voice recordings follows French media reports that the black boxes "distinctly show the sound of an explosion during the flight".
Earlier authorities said they are looking through airport cameras for "unusual activity among policemen or staff."
Security officials at Sharm El Sheikh told the Reuters news agency they "want to determine if, for instance, anyone sneaked past security officials or the metal detectors".
US officials have been quoted as saying exchanges had been intercepted of Islamic State militants boasting about bringing down the jet in Egypt, killing all 224 people on board.
British transport secretary Patrick McLoughlin has said information obtained by the UK indicated there was a "high probability" that the Metrojet aircraft crashed as a result of a bomb, although he pointed out final confirmation was awaited.
It comes as Egypt's foreign minister Sameh Shoukry said countries have not shared intelligence with Cairo about the crash and did not heed Egypt's calls for greater coordination to fight terrorism.
He said: "The information we have heard about has not been shared with Egyptian security agencies in detail. We were expecting that the technical information would be provided to us."
It also emerged a British jet - full of holidaymakers - was involved in a near-miss with a missile close to Sharm el Sheikh earlier this summer.
Meanwhile, airlines are planning to reschedule rescue flights to bring the remaining stranded Britons back from the holiday resort.
It follows the chaos seen on Friday when 21 of the 29 scheduled services were cancelled by the Egyptian authorities with some planes were forced to divert mid-flight.
Returning tourists have hit out at the "absolute shambles" at Sharm airport.
EasyJet said it has two planes due to fly into Luton, while British Airways has one flight scheduled to land at Gatwick.
Monarch expects to operate two services to Manchester Airport.
Thomson Airways said that "due to a last-minute change in Egyptian government restrictions" it could only operate two of its four planned services on Friday.
A spokesman added that two planes are currently on standby in Egypt waiting for slots.
Passengers coming back are not allowed to bring any hold luggage with them, and Egypt's civil aviation minister said the volume of luggage left behind had disrupted operations at the airport.
The US has also tightened security on planes departing from Egypt, while Russia has followed the UK in suspending flights.
However, Vladimir Putin insists this is not because he is convinced of the bomb theory.
French television channel France 2 reported that the black boxes from the plane "distinctly show the sound of an explosion during the flight".
It is claimed that US officials reported chatter between Islamic State leaders in Sinai and Syria about the Egypt plane, and discussions included boasts about taking down an airliner and how it was done.
"They were clearly celebrating," the US broadcaster NBC reported, citing US officials.
It has been announced Britain will set up a small military operations team in Egypt to monitor extremism in the region.
The Minister for Foreign Affairs is urging any Irish citizens in Egypt who may be concerned about developments to contact the Irish Embassy in Cairo.
Minister Charlie Flanagan says his department has provided advice to a very small number of citizens who have made contact with the Consular Assistance Unit in Dublin or the Embassy of Ireland in Cairo seeking information.
He says there are currently no Irish tour operators with package holiday groups in Sharm El Sheikh.
The Department of Foreign Affairs is continuing to monitor the situation in Egypt through the Embassy in Cairo and is in close contact with EU colleagues.
They will continue to review and update travel advice as appropriate.
It is estimated that there are as many as 170 Irish people in Egypt.
The Egyptian Ambassador to Ireland has condemned a decision to halt Irish airlines operating to and from Sharem el Sheikh Airport until further notice.
