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 firm’s 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 Corzine’s 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.

Those in the agriculture business use such firms to help reduce their risks in an industry vulnerable to swings in oil, corn and other commodity prices.

Corzine, a former New Jersey senator and governor, told lawmakers in December that he never instructed anybody to misuse customer money.

O'Brien was among several MF Global officials Wednesday to claim little to no knowledge about the activities of the firm in its final days, including who ordered the transfer of customer funds to cover losses.

Henri Steenkamp, chief executive officer for MF Global Holdings Ltd., testified that he had no knowledge about specific transactions about the money transfer Oct. 26 and the bankruptcy filing because of his "global role" and because he was engaged in "other serious matters."

Subcommittee Chairman Rep. Randy Neugebauer and other lawmakers grilled Steenkamp and other executives about whether such a money transfer was legal and on other issues.

"Just answer the question, yes or no," Neugebauer, R-Texas, told Neugebauer.

"This is a hearing, not a trial," he added. "We're just trying to learn how a 228-year-old company came to its demise."

The Associated Press contributed to this report.