Elizabeth Warren, the architect of the Consumer Financial Protection Bureau, is still worried about the nation's banking system three years after the 2008 meltdown. Warren, who serves as a special assistant to President Obama and special adviser to the Secretary of the Treasury, is tasked with building the CFPB into a key federal entity that shapes how the mortgage finance market works in the future. The bureau is set to open in July. "I think there are parts [of the system] that have changed, but I still worry, a lot," she told Yahoo! Finance's Tech Ticker. "We have more concentration in the banking industry than we had before [and] we're going to have a ‘too big to fail' problem lurking around the edge of this financial system until we've demonstrated how we're going to deal with financial institutions who take on too much risk." Warren's comments followed Treasury Secretary Timothy Geithner's request for Congress to pass legislation that will reform Fannie Mae and Freddie Mac within the next two years. The Treasury released a white paper on how to reform the housing markets in February. All of the plans proposed suggest a move to a mortgage market that is predominately supported by the private sector with a gradual winding down of the GSEs. Write to Kerri Panchuk.