MONTREAL -- The Quebec man whose vehicle was linked to an Amber Alert case last week remained missing on Tuesday despite intensive searches by Quebec's provincial police.

Police spent a fifth day looking for Yvon Lacasse, 71, along a roughly 100-kilometre stretch of highway between Val-d'Or and Rouyn-Noranda in northwestern Quebec, said Sgt. Marc Tessier.

Tessier said officers, canine units and a helicopter were involved in the search operation.

Lacasse, of Lachute, Que., hasn't been heard from since his car was stolen late Thursday at a rest area in that town about 80 kilometres northwest of Montreal.

The following day, Ontario provincial police found a missing boy involved in an Amber Alert inside Lacasse's stolen vehicle southwest of Renfrew, Ont.

They arrested the child's father, who remains in an Ottawa hospital in a coma, according to his lawyer.

Tessier said police retraced a route to Rouyn-Noranda, where the father stayed at a motel early Friday.

The father was charged with second-degree murder on Monday in the slaying of the boy's mother, who was found in a home in Saint-Eustache, Que.

Lacasse is described as bald with brown eyes, five feet, five inches tall, and weighs roughly 100 pounds.