Tokio Marine & Nichido Fire Insurance Co., the nation's top casualty insurer, withheld car insurance payments in up to 100,000 cases in the early 2000s and kept the fact secret despite knowing about it through an internal probe, company officials said Thursday.

The insurer did not disclose cases of unpaid auto insurance money that occurred between April 2002 and June 2003 because its policy at the time was to pay out only if customers made claims, the officials said.

But questions remain about the insurer's assertion because its terms do not say policyholders must make specific claims. The company says it will pay those who missed out on payouts if they make claims now.

The cases of unpaid insurance money concern an accessory policy under which Tokio Marine would pay customers ¥100,000 in condolence money for victims in cases of death and between ¥10,000 and ¥20,000 in cases of injuries resulting in hospital visits or hospitalization.

The insurer looked into cases of unpaid insurance money between April 2002 and June 2005 at the instruction of financial regulators after the industrywide practice of withholding insurance money drew public scrutiny in 2005.

In disclosing the results of its probe on two occasions between 2005 and 2006, the insurer admitted withholding insurance payments in a total of about 63,000 cases but did not disclose the fact that it had withheld insurance payments in up to 100,000 cases.

In July 2003, Tokio Marine changed its rules, deciding to contact customers and pay them if they simply make claims over auto accidents, not specifically for the accessory policy.

The officials said that as a result, the insurer only made public about 18,000 cases of unpaid auto insurance under the accessory policy that arose between July 2003 and June 2005.