By Hend Kortam and Menna Zaki

CAIRO, Nov. 4 (Aswat Masriya) - The Sinai-based militant group Ansar Bayt al-Maqdis said it will reveal the mechanism used to bring down the Russian civilian flight "in its own time" in an audio purported to belong to the group Wednesday. 

On Saturday, an Airbus A321 operated by a Russian airliner crashed in the Sinai desert, where the militant group has been based for at least two years, launching attacks across the country. 

The group claimed responsibility for the attack in a statement circulated on social media on the day of the plane crash but the claim has since been dismissed locally and internationally.

In the audio, which Aswat Masriya could not independently verify, the group says "we, thanks to Allah, are the ones who brought it down and we are not obliged to reveal the mechanism." 

Ansar pledged allegiance to the Islamic State fighters in Syria and Iraq on November 10, 2014 rebranding themselves as "Sinai Province". According to the recording, the downing of the Russian plane comes exactly one year from the time they pledged allegiance to ISIS which was on 17 Moharam, 1436 on the Islamic calendar.

The Russian plane was brought down on 18 Moharam 1437.  

President Abdel Fattah al-Sisi had told the BBC in an interview on Tuesday that Ansar's claim Saturday that it was responsible for the attack was propaganda. The Russian ambassador to Egypt has declined to comment on the statement and officials from both sides said the cause of the crash cannot be discerned before an investigation is complete.  

The black boxes were recovered on the day of the crash and the contents of the flight recorders are currently being analysed. An initial reading of the contents showed that "uncharacteristic sounds" were heard in the cockpit at the time of the plane's disappearance, Interfax news agency said. 

Discrediting the investigation, however, Ansar challenged the investigations saying "bring the plane wreckage, search it. Recover the black box and analyse it. Come out to us with the summary of your research and prove that we did not bring it down." 

The plane disappeared from radar at 31,000 feet as it was cruising, raising doubts that the militant group has the capacity to strike it at this distance. Yet, one thing analysts agreed on was that the Russian charter flight was torn apart mid-air. 

Global intelligence firm Stratfor dismissed in an online report published Nov. 2, the possibility that the plane was shot down by militants, adding that the "most probable explanation for the downed plane is the existence of an explosive device onboard." Stratfor cited the "poor" state of security that Sharm el-Sheikh airport, where the plane took off, is known for.

Amid a flood of theories on the cause of the crash, James Clapper, the director of U.S. National Intelligence told a conference on Monday that there was no "direct" evidence of terrorist involvement yet, a NBC news video showed. 

The Russian plane carrying 224 passengers including crew members, was flying from Sharm el-Sheikh to St. Petersburg. It disappeared from the radar 23 minutes after it took off. The plane crash left no survivors. 

Militancy inside Egypt has seen a significant rise since the military ouster of Islamist President Mohamed Mursi in July 2013, following mass protests against his rule. 

North Sinai is at the epicentre of the insurgency and most attacks target security forces there.

The crash is raising fears of further harming Egypt's tourism sector, which the Egyptian state has been trying to revive over the past five years.