The Washington Monument has closed again following problems with its elevator.

National Park Service spokesman Mike Litterst said in a statement that the service interruption happened just before 11:30 a.m. Wednesday. Litterst said one employee was on board but no visitors. The statement says 84 visitors walked down the stairs without incident and that the cause of the interruption is unknown.

Litterst says the monument will remain closed pending an inspection by technicians.

The monument closed over the weekend as a result of a voltage drop of incoming power to the monument. The monument closed early Saturday night and all day on Sunday but re-opened Monday.

The monument was closed for nearly a week in July because of elevator problems.