The biological father in the abduction case of Abby and Dominic Maryk has been extradited from Mexico back to Winnipeg.

Kevin Maryk, 41, was arrested in Guadalajara, Mexico, in May, when authorities found Abby and Dominic near a townhouse complex in the city.

He is being detained in custody on two counts of abduction and two counts of conspiracy to commit an indictable offence.

"Being extradited from one country to another is not a simple task," Winnipeg police Patrol Sgt. Monica Stothers said Friday.

"There's different levels of government and law enforcement that's involved in it."

The children were five and seven years old, respectively, when they went missing in August 2008.

Police allege that they were on a two-week vacation as part of a court-approved visit with their father, then fled Canada and were never returned to their mother, Emily Cablek, who has legal custody.

Maryk lived for a while in Peurto Vallarta, Mexico and then Guadalajara, police said, keeping the kids indoors during the day and preventing them from going to school.

Investigators got a break in the case last May, when a neighbour in Guadalajara called authorities after recognizing the children in a Crime Stoppers video that aired in Mexico. The kids were then brought back to their mother in Winnipeg.

Police have also charged three other people in the case. Robert Groen, 41, was arrested in Mexico on conspiracy charges on July 19 and has been returned to Winnipeg for prosecution.

Darlene McKay, 53, and Bradley McKay, 48, who are relatives of Maryk, have been charged with obstruction of justice.

At last word, investigators were still looking for Cody McKay, who is Kevin Maryk's nephew and the son of Darlene and Bradley.