Kano - A Russian cargo plane that Nigerian authorities detained on Saturday had no weapons on it but was carrying two French army helicopters out of Central African Republic, the French ambassador said on Monday.The Antonov 124 had been travelling from Bangui to the Chadian capital N'Djamena but made an emergency landing in Kano because of traffic congestion at N'Djamena airport, the statement from Jacques Champagne de Labriolle said, adding that Kano was the "closest airport facility".The plane was allowed to take off from Kano on Monday evening, the Russian embassy in Nigeria said on its official Twitter account.Nigerian authorities detained it on arrival and questioned its French crew. A Nigerian security source said that in addition to two helicopters, there was also a bullet-proof jeep and boxes of suspected military hardware, without giving further details.Nigerian authorities have not responded to repeated requests for comment on the incident since Saturday.Two French non-commissioned officers were escorting the Gazelle helicopters, Labriolle said."The shipment is organised as the size of the French military intervention in CAR (Central African Republic) is being reduced," he said. "The Nigerian federal and airport authorities, being satisfied with the documents and the genuine character of the flight, have announced that the plane will be authorized to pursue its flight to N'Djamena."The plane was still in the airport at around 13:00, a Reuters witness said."There was absolutely no weapon, and no ammunition on board the aircraft," Labriolle said.He added that the transfer was "part of the French effort to support regional co-operation against terrorism" in Nigeria, Niger, Chad and Cameroon, all of whose border areas around Lake Chad are plagued by Islamist militant group Boko Haram.