Bond insurer Assured Guaranty fired off a lawsuit against OneWest Bank, claiming the successor to IndyMac is not appropriately servicing mortgage loans that Assured Guaranty insures, Courthouse News Service reported.

The insurer claims OneWest's failure to deal with the underlying mortgages has cost Assured Guaranty $355 million.

In the suit, Assured Guaranty accuses OneWest of not following terms laid out in various pooling and servicing agreements.

Courthouse New Service says Assured wants OneWest to be terminated as its mortgage servicer. In addition, the bond insurer is demanding the bank open its books, so Assured Guaranty can review various mortgage documents.

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