"A man with that name has applied for a residency permit," spokeswoman Irene Sokolow told AFP, confirming Sonko's birth date in his application.
His application was dated September 21.
Gambian President Yahya Jammeh fired Sonko on Sunday and replaced him with a military officer previously convicted of plotting a coup against him, in the latest unpredictable move from the west African strongman.
Jammeh is expected to win a fifth term in a December election. His regime is regularly accused by rights groups of arranging the forcible disappearance of opponents.
Sonko had served as interior minister since 2006 – except for a brief 2012 appointment as ambassador to Spain, a decision that Jammeh reversed one week later.
He was previously a member of the presidential guard and protected Jammeh when he was threatened with a coup attempt in 2000, rather than joining other guards mounting an insurrection.