Investigators have extracted the content of at least one of the two black boxes recovered from a Russian airplane that crashed in Egypt over the weekend, Egypt’s Civil Aviation Ministry said Wednesday, Reuters reported. A second black box with audio from the cockpit was partially damaged, and it was expected that it would require extra time to extract and validate the data.

The black boxes are likely to be critical in learning what happened to Airbus A321M, which crashed Saturday in Sinai shortly after it began its journey from Sharm al-Sheikh en route to Russia. All 224 passengers on board died in the crash.

Local press reports indicated that the recorders had picked up abnormal sounds before the crash, but Civil Aviation Minister Hossam Kemal said it was too early to say what happened on board. "This is all speculation. There is nothing definitive until the investigation commission completes its probe," he said.

Militants affiliated with the Islamic State group, also known by ISIS, have taken responsibility for the attack. Egyptian President Abdel Fattah el-Sisi has discredited such claims as “propaganda.” A video surfaced Wednesday appearing to show ISIS fighters brandishing smiles and bowls of candy in celebration of the plane crash.

Sinai Province, an Egyptian group that has pledged allegiance to the Syria- and Iraq-based militants, said they would tell the world soon how it carried out the attack. The group has been responsible for routine violence in Egypt’s restive Sinai region in recent years.

The militants, however, are not believed to have technology capable of destroying an airplane in flight, and U.S., Russian and Egyptian officials have cast doubt on their claims. Russian officials said the plane seemed to have broken up in the air. Some have speculated that there may have been technical difficulties or an explosion on board.

Russia intervened in Syria late September in hopes of bolstering the Syrian President Bashar Assad. The group has repeatedly made threats to target Russia’s interests in response to their bombing of ISIS targets in the country. Fighters with the militant group, insisting that they were responsible for Saturday's plane crash, said in a video Tuesday that more attacks were to come.