'The Dark Knight' actor died of an accidental drug overdose in January this year, but Reliastar Life Insurance is investigating whether he committed suicide.

Lawyers for Matilda Rose -the star's daughter with 'Brokeback Mountain' co-star Michelle Williams - are suing the firm, insisting there is no evidence of suicide.

If they win, the three-year-old could also be entitled to an additional $62 million in damages.

Prosecutor William Shernoff said: "The money belongs to Matilda. There's not a shred of evidence that points to suicide.

"If the court found that the insurance company was acting in bad faith, they could add punitive damages - that would amount to four or five times the insurance policy."

A New York City inquest previously ruled the death was a tragic accident.

Earlier this week, Ledger's father Kim announced Matilda would receive the star's entire estimated $16.6 million estate - but she could end up getting next to nothing - or more than she ever dreamed, depending on how the insurance company's investigation goes.

The star left his fortune to his parents and three sisters, but the family have confirmed they will be passing everything to Matilda. (c) BANG