Lohan's alarm set off; it's unclear why

LOS ANGELES, June 3 (UPI) -- Los Angeles probation officials visited Lindsay Lohan's house this week because her house-arrest electronic monitoring device went off.

Lohan, 24, is under house arrest for violating her probation for a drunken driving conviction by stealing a $2,500 necklace. She was sentenced May 11 to 120 days in jail, but was eligible for home confinement because of jail overcrowding.

The Los Angeles Times said it is unclear why her monitoring device sounded an alarm Tuesday, but the newspaper reported investigators were dispatched to determine whether there was a system malfunction or Lohan strayed outside the boundaries set up for her by the court.

The "Mean Girls" and "Freaky Friday" star has been spending her time under house arrest watching TV, reading scripts and posing for tabloid photographs on her rooftop patio, the Times said.