The National Park Service announced Monday it would close access to inside the Washington Monument indefinitely, The Washington Post reported.

The agency cited “ongoing reliability issues” with the elevators going to the top of the monument and made the call to close access to the top of the obelisk until the elevators are fixed, according to The Post.

“As a result, we have made the difficult decision not to reopen the Washington Monument until we can modernize the elevator control system,” the service told The Post.

Mike Litterst, a spokesman for the National Park Service, told the Post that “it’s a long-term closure, one that will be measured in months.”

After on-and-off elevator service for the past few months and a month-long investigation about elevator problems, officials said they were not able to determine the exact problem with the monument’s lone. National Park Service officials listed several potential reasons for the problems, including the elevator is 15 years old and its mechanical and electrical systems are worn out, The Post reported.

The monument closed for about three years after an earthquake damaged the structure in 2011.