Actress Lindsay Lohan, currently serving what is expected to be about 35 days under house arrest for that theft of a necklace from a Venice, Calif., jewelry store, may not be as easy to keep track of as authorities thought.

Her electronic-monitoring system apparently went off this week and had to be replaced, the Los Angeles Times reported. The replacement has been made, and Lohan continues to be confined to her home, according to the report.

The ankle device reportedly went off on Monday for unknown reasons. Law enforcement authorities paid a visit to check it out.

"They came as part of standard procedure to make sure the monitoring equipment was working properly," said Lohan’s spokesman, Steve Honig, in a statement.

Shawn Chapman Holley, Lohan’s attorney, added: "Lindsay’s electronic monitoring system went off on Monday. When a representative from the monitoring company went to her home, the representative found Lindsay there. The equipment was replaced the following day."