When Cologne artist Gunter Demnig installed his first "stumbling block" Holocaust memorial in Berlin 17 years ago, he could not have imagined that his idea - to place plaques on the pavements in front of buildings that once housed Shoah victims - would spread throughout Germany and other European cities.

Mr Demnig said there were now around 48,000 stumbling block memorials (Stolpersteine) across Europe.

This week, Mr Demnig helped install a new brass plaque in the town of Völklingen, in the state of Saarland, dedicated to all the slave labourers forced to work in the Völklinger Hütte, an iron and steel factory. The factory was established in the mid-19th century and last used in 1986.

According to local reports, about 100 residents of Völklingen turned up for the ceremony, in which an elongated brass block was installed in front of the former factory.

Hubert Kesternich, a member of a local activist group that co-sponsored the memorial, said that between 1942 and 1944, 219 adults and 35 children died at the factory as a result of malnutrition, disease and the terrible working conditions.

Donations to the project can be made at www.stolpersteine.eu/en. A gift of 120 euros covers the cost of one plaque.