Updated

Authorities at the Auschwitz-Birkenau State Museum are warning that the number of visitors to the former German death camp is growing so high that they might have to start turning people away.

The memorial site on Wednesday urged potential visitors to book their visits online ahead of time to prevent that from happening. It said there have been more than 250,000 visitors so far this year, a rise of more than 40 percent compared with the same period last year, which itself hit a record with 1.5 million visitors.

Andrzej Kacorzyk, a deputy director, said there have been long waits recently to enter at certain hours.

In January, officials marked the 70th anniversary of the camp's liberation, a possible reason for the surge in interest.