Berlin's Holocaust memorial at risk of crumbling BERLIN (Reuters) - German authorities have started reinforcing hundreds of concrete blocks at Berlin's Holocaust memorial with steel collars after a study revealed they were at risk of crumbling. The memorial to Jews killed in World War Two has become one of Berlin's most popular tourist attractions, drawing coach loads of visitors each day to wander through the maze of gravestone-like blocks a short walk from the Brandenburg Gate. A survey by engineers found about 1 in 7 of the 2,711 blocks is in danger of breaking up due to cracks in the concrete. "We aren't sure why there are cracks in the blocks but it could be to do with extreme fluctuations in temperature and the weather," said memorial foundation spokeswoman Felizitas Borzym. The design and construction of the memorial have been plagued by controversy. Building work was briefly halted in 2003 when it emerged the parent firm of Degussa, the company supplying anti-graffiti paint for the blocks, manufactured the poison gas used in Nazi death camps. Since its unveiling in 2005, the 27 million euro monument has shown increasing signs of wear and tear. Steel collars have been fitted around two of the blocks to prevent chunks from falling off, and the foundation said they expect this to be extended to another 380 blocks soon. "We didn't want to close off the memorial, so the steel collars mean we can monitor the blocks and make it safe for visitors," she said.