A top former MF Global executive declined to testify Wednesday during a House hearing on whether she approved or had knowledge that CEO Jon Corzine approved a transfer of nearly $200 million in customer funds to cover losses days before the brokerage firm collapsed.

Edith O'Brien, the firms former assistant treasurer, invoked her Fifth Amendment rights to not testify.

Her appearance before House Financial Services' oversight subcommittee came after congressional investigators recently acquired an email contradicting Corzines testimony that he did not order the transfer.

O'Brien also decline to comment on a published report that she is seeking immunity for her cooperation in an investigation.

The firmed file for bankruptcy Oct. 31 after a disastrous bet on European debt. It was the eighth-largest bankruptcy in U.S. history and resulted in farmers, ranchers and other customers losing roughly $1.6 billion.