Felicity Huffman and Lori Loughlin have been charged along with 48 others in a massive bribery scam involving some of the most elite colleges in the country. Court records show the actresses and others allegedly paid hefty bribes -- as much as $6 MILLION -- to get their kids into various schools, including Yale, Stanford, Georgetown and the University of Southern California. The charges include conspiracy to commit mail fraud and honest services mail fraud. We've learned Felicity has been arrested and is presently in custody. We're told she will be released on a signature bond ... which essentially is a promise to appear in court. The alleged scam was reportedly unearthed after authorities found a California businessman who ran an operation helping students get into the college of their choice. Authorities say parents would pay the man a predetermined amount which he would funnel to an SAT or ACT administrator or a college athletic coach. The feds say if the money went to a college coach ... the coach would arrange a fake profile that listed the student as an athlete. If the money went to an exam administrator, the administrator would either hire a proctor to take the SAT/ACT or correct the student's answers. As for Loughlin, she and her husband -- Mossimo Giannulli, the founder of Mossimo clothing -- reportedly paid $500,000 to have their 2 daughters designated as recruits for the crew team at USC ... despite the fact they did not actually participate in crew. Mossimo was also charged in the indictment. As for Huffman, she and her husband, William H. Macy, reportedly made a charitable contribution of $15,000 to participate in a college entrance exam cheating scheme on behalf of their eldest daughter. Macy was not indicted. And the federal indictment out of Boston has a twist ... it says most of the kids admitted to the schools had no idea their parents allegedly greased the wheels to get them in. We reached out to the reps for both Felicity and Lori ... so far no word back.