Federal officials say they're investigating the sudden and mysterious closure of a for-profit vocational school in Bridgeport.

Butler Business School's 227 students were stunning to hear that the school has closed its doors indefinitely. Some are left wondering if they'll ever get their diplomas, or get their money back.

Students say the way in which the school was closed was particularly shocking. Teachers hurried to pack up bags and boxes, and students discovered a note on a door that advised them to call the school's corporate offices.

Butler had offered 13-month courses in medical and business programs. Many students say they've taken out $20,000 loans and invested months of their time into the school, only to see it abruptly shuttered.

Sen. Richard Blumenthal (D-Conn.) says he has written a letter to school officials to notify them that they must refund students' tuition or have a system in place to allow students to transfer credits to other schools.

Blumenthal says students who are seeking answers should contact his Hartford office by calling (860) 258-6940.