Ten police detectives in an anti-kidnapping unit are on the case and believe 54-year-old Maura Villarreal is still being held hostage. Police said the strategy of making no contact is a common ploy used by kidnappers in the South American country.
Urbina's mother disappeared from her home on the outskirts of Caracas on Sept. 1. Police have said they believe she was taken by four men who arrived wearing police uniforms.
Police also have said they believe a mechanic who happened to be working on a motorcycle at the house was taken away along with Urbina's mother.
A senior police official, speaking on condition of anonymity, said it had been difficult for the family to accept police involvement because they fear for Villarreal's life.
The official confirmed Venezuelan news reports that the amount of ransom demanded was about $3 million, but he also said the figure had varied over time and that initially the kidnappers had demanded $6 million.
Urbina left the Tigers in September to travel to Venezuela following his mother's disappearance. He has declined comment on the case.
On Nov. 5, Detroit exercised a $4 million option on the reliever, who was 4-6 with a 4.50 ERA and 21 saves in his first season with Detroit.
Urbina, ninth in the AL with 21 saves, has a record of 39-43 with a 3.42 ERA and 227 saves in 10 seasons.