Police sources revealed on Tuesday that the black boxes were sent to Paris over the weekend for examination.
A Boeing 727 operated by Union des Transports Africains (UTA), which is registered in Guinea, crashed into the sea on takeoff from Cotonou, the main city in Benin, killing 139 of the 161 people on board.
Most of the passengers were Lebanese expatriates returning home for the holidays.
France sent experts to its former colony following the crash, but Benin does not have the technology to decipher data on flight recorders.
Benin, with the assistance of Lebanon, has launched a full-scale investigation into the crash, the worst in the history of both Beninese and Lebanese civil aviation.
Plane carried excess wieght
Several unofficial sources suggest that the plane was unbalanced and carried at least eight tonnes in excess of its capacity, Lebanese media have reported.
Preliminary investigations into the cause of the crash suggest it was due to pilot error.
Meanwhile, Lebanon has told the authorities in Guinea that it wants to question a Lebanese national, allegedly arrested in Conakry recently, in connection with the Christmas Day crash.
"We have received information indicating that Darwish al-Khazim was apprehended in Conakry. We have asked Interpol to inform Guinea that the Lebanese judiciary has decided to interrogate him in connection with the inquiry into the crash in Cotonou," Attorney General Adnan Addoum told the Lebanese press late on Monday.
Al-Khazim, one of the UTA bosses, was among 22 survivors of the crash. He was repatriated to Beirut for treatment after the crash but only remained in hospital briefly before heading to London for talks with Lloyds insurance underwriters, his father Ahmad, a former stake-holder in UTA, has said.