Two top executives of a bankrupt solar panel company appeared before a U.S. congressional hearing Friday, but invoked their right not to answer questions.

Members of House Energy and Commerce Committee questioned Solyndra chief executive Brian Harrison and chief financial officer W.G. Stover about the federal loan guarantee the company received before going bankrupt.

But Harrison and Stover invoked their constitutional right not to answer questions that would incriminate them personally.

Solyndra Incorporated received a $528 million loan from the government in 2009. In July of this year, top executives testified to Congress that the company was prospering. But earlier this month, the California-based company filed for bankruptcy, laying off more than 1,000 workers.

One lawmaker compared the half-billion dollars in lost loan funding to a train robbery.

The case has been embarrassing for the Obama administration, which had held up the company as an example of desirable “green” technology and job creation.

An investigation continues into the company and its ties to the federal government's Department of Energy.