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 coming home from 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 A320-200 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 on Wednesday spoke 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.

Egyptian officials have condemned Britain’s travel ban as an overreaction. Egyptian President Abdel-Fattah el-Sissi was in London on a state visit Thursday, facing what is likely to be a tense meeting with British Prime Minister David Cameron.

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.

Egyptian Antiquities Minister Mamdouh Eldamaty rejected the U.S. and British allegations outright.

“(The crash) not a terror act. It was an accident,” he declared Thursday, speaking at the ancient city of Luxor 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 presidential spokesman, Alaa Youssef, also said Egyptian authorities wish the U.S. and Britain had “waited for the result of the ongoing investigation.”

Metrojet has 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 from the resort 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.

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 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 required in order 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 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 victim of the crash was buried Thursday after a church service in a whitewashed 16th-century church overlooking the Volkhov River.

Family and friends came to say their goodbyes to Nina Lushchenko, 60, who worked in a school canteen all her life. They remembered her as a good mother and grandmother.

Her daughter told the Russian LifeNews television channel earlier this week that Lushchenko had considered taking her granddaughter with her on vacation but later decided against it.