The elaborate plot involved two Mexicans, a Canadian and a Danish suspect who allegedly tried to smuggle in the younger Qaddafi and his family under false names and false Mexican document, said Interior Secretary Alejandro Poire.
The plot was uncovered in early September as al-Saadi was fleeing Libya after his father's ouster. He never made it to Mexico. Al-Saadi Qaddafi fled Libya and is living in the Western African country of Niger.
The plotters allegedly jetted into Mexico, opened bank accounts and bought properties meant to be used as safe houses in several parts of the country, including one at the resort of Bahia de las Banderas on Mexico's Pacific coast.
"The large economic resources which this criminal organization has, or had, allowed them to contract private flights," Poire told a news conference.
Poire said the leader of the plot was a Canadian woman he identified as Cynthia Vanier. He said she had been detained on Nov. 10 and is being held, along with three other suspects, under a form of house arrest on suspicion of falsifying documents.
An employee of Canada's foreign ministry said the office would look into the report of the arrest but had no immediate comment.
Based on reporting by The Associated Press.