10 Downing Street issued a statement suggesting a bomb might have caused the destruction of a Russian plane that crashed over the Sinai Peninsula, killing all 224 people on board.

“While the investigation is still ongoing we cannot say categorically why the Russian jet crashed,” a Downing Street spokesman said Wednesday. “But as more information has come to light we have become concerned that the plane may well have been brought down by an explosive device.”

The revelation led to numerous groundings of United Kingdom-bound planes from Egypt.

“In light of this, and as a precautionary measure, we have decided that flights due to leave Sharm for the UK this evening will be delayed,” they continued. “That will allow time for a team of UK aviation experts, currently travelling to Sharm, to make an assessment of the security arrangements in place at the airport and to identify whether any further action is required. We expect this assessment to be completed tonight.”

The plane crashed on Saturday. The Islamic State (ISIS/ISIL) radical Islamist group claimed responsibility for the tragedy. ISIS-linked organization Wilayat Sinai–formerly Ansar Bayt al-Maqdis–posted a statement on social media, declaring, “The fighters of the Islamic State were able to down a Russian plane over Sinai province that was carrying over 220 Russian crusaders. They were all killed, thanks be to God.”

Russian and Egyptian officials immediately dismissed its claim.

Russian propaganda outlets are reporting the injuries suffered by the passengers point to an explosion on the plane.

“A large number of body parts may indicate that a powerful explosion took place aboard the plane before it hit the ground,” an Egyptian forensic expert told Sputnik.

The Egyptian Civil Aviation Ministry explained to the media that they cannot “talk about the results as we go along” and warned it “could be a long process.” Egyptian cabinet spokesman Hossam al-Kawish said that “it could take between one and four weeks” to analyze the plane’s recorders.

The Metrojet Airbus A321-200 crashed on Saturday, killing all 224 people. Metrojet Deputy Director Alexander Smirnov told the media “an external impact on the airplane” is the only way the airplane could have come down. But Alexander Neradko, Russia’a top aviation official, said Smirnov’s comments were “premature and unfounded.”

U.S. officials claimed satellite imagery shows a heat flash immediately before a Russian plane crashed into Egypt’s Sinai Peninsula.

“The speculation that this plane was brought down by a missile is off the table,” declared one official.

The official told NBC News that the imagery led experts to “believe it could have been some kind of explosion on the aircraft itself, either a fuel tank or a bomb.” More than likely “the plane disintegrated at a very high altitude.”

“The number of heat signatures is crucial,” explained CNN aviation analyst Miles O’Brien. “If, in fact, only one was detected, that in some respects might steer one away from a missile launch and onto some idea of an explosion on board the aircraft.”