Sources said Thursday the Securities & Exchange Commission is moving toward charging former and current executives at Fannie Mae and Freddie Mac for violations related to the financial crisis. But the charges could lead to a clash with the Federal Housing Finance Agency, which has overseen the companies since they collapsed in 2008 and whose officials do not think either company violated the law. The SEC alleges that at least four senior executives misled investors as the housing market fell by failing to provide the companies’ mortgage holdings. Over the past eight weeks, the SEC sent notices to executives saying they may face civil charges, which differ slightly for each company. If the companies are charged and must defend themselves, the cost will be paid by taxpayers as the companies were taken over by FHFA in 2008.