Heath Ledger's insurance company has refused to pay on his $10 million policy by claiming he died under "suspicious" circumstances - and now wants to quiz his friend Mary-Kate Olsen over his death, a lawsuit filed by the "Dark Knight" star's estate charges.

Lawyer John LaViolette, who represents the trust set up for Ledger's 2-year-old daughter, Matilda, has sued ReliaStar Life Insurance Co., accusing it of acting in bad faith by trying to avoid paying the claim and wrongfully snooping into the actor's life.

The city medical examiner ruled that the 28-year-old "Brokeback Mountain" star died of an accidental overdose of prescription drugs - but probers working for ReliaStar are investigating the possibility he took his own life, which would void the claim.

ReliaStar has informed Matilda's lawyers that it intends to take depositions from Olsen, as well as the masseuse who was at Ledger's SoHo apartment when he died, and his agents and doctors.