The Washington Monument will be closed indefinitely because of ongoing problems with its elevator, the latest in a series of woes for one of the city’s most enduring tourist attractions.

The National Park Service said in a statement Monday that the monument will remain closed until its elevator control system can be modernized, a process that’s expected to take up to nine months once work begins. A start date for the project has not been determined.

The lone elevator that takes visitors to the top of the 555-foot obelisk has broken down frequently over the past two years, roughly since the monument reopened after being damaged in an earthquake.

Park service officials have said they don’t believe that the 2011 earthquake caused the elevator problems. But they don’t know exactly what’s wrong with it. Despite a monthlong inspection, “we have not been able to determine the cause of the ongoing reliability issues,” the park service said.

Del. Eleanor Holmes Norton, a Democrat who represents the District of Columbia in Congress, said in a statement that the timing of the closure “could not be worse,” given the crowds that have flocked to Washington for the opening of the Smithsonian’s National Museum of African American History and Culture, which is next to the monument.

“We have grown so accustomed to the repeated closures that unless there is some danger to the public, the monument should be open to the public for as long as possible,” Norton said.

Mike Litterst, a park service spokesman, said the elevator is safe, but the breakdowns present an ongoing inconvenience.

“There are other factors in play when we have service interruptions. When it gets stuck, people are stuck inside there for 40 minutes to an hour in cramped, closed quarters,” he said. “We couldn’t put visitors or staff at risk by attempting to reopen, knowing it was likely going to happen again.”

The park service hopes to announce a timetable for the renovation project, which is expected to cost up to $3 million, within the next few weeks.

In the meantime, it’s possible that limited groups of people might be given the opportunity to walk the staircase to the top of the monument, but that option won’t be made available for the general public, Litterst said.

“We certainly share the frustration and the disappointment of the visitors,” he said.

(AP)