VELIKY NOVGOROD, Russia (AP) -- Russia and Egypt on Thursday dismissed suggestions by Britain and the United States that a bomb was likely to have brought down a Metrojet flight packed with Russian vacationers leaving an Egyptian resort, saying the claim was premature.
A spokesman for Russian President Vladimir Putin, Dmitry Peskov, insisted that aviation investigators were working on all possible theories as to why the Airbus A321-200 carrying 224 people crashed Saturday in Egypt's Sinai Peninsula, killing everyone on board. He said naming just one possibility was mere speculation.
"One cannot rule out a single theory, but at this point there are no reasons to voice just one theory as reliable --- only investigators can do that," Peskov told reporters in Moscow.
British Foreign Secretary Philip Hammond spoke Wednesday of a "significant possibility" the crash was caused by a bomb and Britain immediately suspended all flights to and from Sharm el-Sheikh, the Red Sea resort where the flight originated. The move stranded hundreds of tourists in Egypt.
In London on Thursday, British Prime Minister David Cameron said the crash was "more likely than not" caused by a bomb. He said he had "every sympathy" with the Egyptians, who rely so on heavily on tourism, but that he had to "put the safety of British people first."
He says British officials are not yet certain the plane was bombed, but it's a "strong possibility."
Cameron said he would call Putin later in the day to discuss the crash.
Egyptian officials have condemned Britain's travel ban as an overreaction. Egyptian President Abdel-Fattah el-Sissi was in London on a visit Thursday.
Russia's top aviation official, Alexander Neradko, said in televised remarks Thursday that investigators are pursuing several theories as to why the plane crashed. He said they are looking for traces of explosives on the victims' bodies, their baggage and the plane debris as well as studying other "aspects linked to a possible terrorist attack onboard."
Neradko said the probe is likely to take several months and called for caution in speculation about the likely causes of the crash.
Asked about Hammond's statement, Russian Foreign Ministry spokeswoman Maria Zakharova said Thursday that if Britain had information about the bomb, it's "really shocking" that it hasn't shared it with Russia. Zakharova urged Britain to immediately provide any such information to the investigators.
Russia state television has skirted the bomb theory, not mentioning the British and U.S. report. Other popular media in Russia are full of speculation about the crash and reports about signs they believe point to foul play.
The plane crashed in the northern Sinai, where Egyptian forces have been battling an Islamic insurgency for years. Islamic State has claimed responsibility for downing the plane but offered no proof. El-Sissi has called the IS claim "propaganda" designed to embarrass his government.
In the ancient city of Luxor on Thursday, Egyptian Antiquities Minister Mamdouh Eldamaty rejected the U.S. and British allegations outright.
"(The crash) is not a terror act. It was an accident," he declared as authorities opened three tombs to the public for the first time in an effort to encourage tourism. "(It's) very sad what happened, but we have to wait for the result of the investigation."
Egypt's minister of civil aviation, Hossam Kamal, insisted Thursday that the country's airports comply with international security standards.
He said that in light of U.S. and British allegations that the Russian flight may have been downed by a bomb, "the investigation team does not have yet any evidence or data confirming this hypothesis."
Metrojet suspended all flights of Airbus A321 jets in its fleet after the crash, the Russian Federal Transport Agency said Thursday. The company has ruled out a pilot error or a technical fault as a possible cause of the crash, drawing criticism from Russian officials for speaking with such certainty too soon.
Intercepted communications played a role in the tentative conclusion that the Islamic State group's Sinai affiliate planted an explosive device on the plane, said a U.S. official briefed on the matter. He spoke on condition of anonymity because he wasn't authorized to discuss intelligence matters publicly.
The official and others said there had been no formal judgment rendered by the CIA or other intelligence agencies, and that forensic evidence from the blast site, including the airplane's black box, was still being analyzed.
The official added that intelligence analysts don't believe the operation was ordered by Islamic State leaders in Raqqa, Syria, but possibly planned and executed by the Islamic State's affiliate in the Sinai, which operates autonomously.
Britain sent a team of security and defense experts to Sharm el-Sheikh, where thousands of British tourists are stranded by the British ban on flights. Hammond says he expects British tourists to be flown back starting Friday, after measures are taken to tighten security at the resort's airport.
"The airline industry is indicating that they expect by tomorrow to be in a position to start bringing people out," Hammond said.
In Sharm el-Sheikh, British tourists said they understand their government's move to suspend flights but were worried about the future of Egyptian tourism. Paul Modley, a 49-year-old Londoner, has travelled to Sharm el-Sheikh seven times in the last nine years.
"We understand why the government have done it, but I am really worried for the Egyptian people because --- particularly in the Red Sea resorts --- they are so dependent on tourism," said Modley.
On the ground in the Sinai, rescue teams have retrieved 140 bodies from the scene and more than 100 body parts. Russian rescue workers, combing a 40 square kilometer (15.4 sq. mile) area, should be finishing their search for remains and wreckage by Thursday evening, according to Emergency Situations Minister Vladimir Puchkov.
Egypt has said the cockpit voice recorder of the Russian plane is partially damaged and a lot of work is going to be required to extract data from it.
Grief continued to roil St. Petersburg and its suburbs, as mourners brought more flowers, candles and paper planes to the city's imperial-era square and the airport where the crashed Metrojet flight had been due to land.
In the ancient Russian city of Veliky Novgorod, 160 kilometers (100 miles) south of St. Petersburg, the first crash victim was buried Thursday after a church service in a whitewashed 16th-century church overlooking the Volkhov River.
Family and friends said goodbye to Nina Lushchenko, 60, who worked in a school canteen, remembering her as a good mother and grandmother.