Paris - The Eiffel Tower in Paris shut down early at 4pm on Wednesday due to strike action, the monument's official Twitter account said.
A spokeswoman for the company running the tower said negotiations with unions were expected to take place and it was not yet clear late Wednesday afternoon whether the tower would reopen the following day.
Earlier, the company had said that a threatened strike had been put off until Thursday.
The CGT trade union said the strike had been called because new queueing arrangements for the tower's lifts had caused crowding and were frustrating staff and visitors alike.
Local mayor Rachida Dati has also complained about growing queues for the security checks around the site.
The queues themselves were a security issue as well as a nuisance for local residents, Dati said in letters to management and police published on Twitter on Tuesday.
Work is currently under way to build new glass and metal fences around the tower.
They will replace temporary security barriers put in place in response to the deadly terrorist attacks that hit Paris in 2015.
More than 6.2 million people visited the Eiffel Tower last year, according to regional tourism authorities.