Malia Obama's Secret Service Agents Detain Man After Marriage Proposal

Malia Obama's day at the office was interrupted by a guy asking her to marry him ... and her Secret Service agents took him into custody because he has a sketchy history with the White House.

Law enforcement sources confirm 30-year-old Jair Nilton Cardoso was detained after he showed up on April 10 at the Weinstein Company offices in Manhattan where Malia is interning. We're told the man held a sign up against an office window that read, "Will you marry me?".

Agents kicked him out, but 2 days later he showed up again outside another building where Malia was working. This time agents recognized him as a guy who'd attempted to get into the White House multiple times.

We're told Malia never felt threatened because her agents were there and, as one source put it ... "she didn't want to make a stink" about the situation. Agents interviewed Cardoso, determined he needed psychiatric evaluation and took him to a hospital.