Eleven Nigerian military personnel are reportedly still in Burkina Faso days after their plane made an “unauthorised” landing in the south-west city of Bobo Dioulasso, despite earlier suggestions they had been freed, deepening confusion about the diplomatic standoff.

Burkinabé authorities told the BBC on Tuesday that the troops had been released and given permission to return to Nigeria, but officials in Abuja have said the matter is yet to be resolved.

The Nigerian daily the Punch quoted Kimiebi Ebienfa, a foreign ministry spokesperson, as saying late on Wednesday that that Nigerian embassy in Ouagadougou was “engaging with the host authorities to secure their release”.

The saga began on Monday when a Nigerian military cargo plane, a C-130, travelling from Lagos to Portugal was forced to land in Burkina Faso. Authorities in the country, which is part of the three-member Alliance of Sahel States (AES), called the landing an “unfriendly act carried out in defiance of international law” in a statement that evening.

The Nigerian air force said technical concerns had forced the plane to divert to the nearest airport “in line with standard safety procedures and international aviation protocols”. The Burkinabé authorities had treated the crew courteously and plans were under way to continue the mission, it said.

Conspiracy theories began circulating on social media and offline given that the landing came within 24 hours of Nigerian troops helping to thwart a coup attempt in Benin, which borders Nigeria and Burkina Faso.

The AES trio of Burkina Faso, Mali and Niger officially left the larger Ecowas regional bloc in January, forming a military alliance as it withdrew from many of its traditional local and international allegiances.