The owner of an asparagus farm in the province of Brabant is being investigated by the Social Intelligence and Investigation Service (SIOD) to see if criminal charges can be brought against her after 50 East European workers were discovered to be living in "near-slavery" conditions.

The SIOD - a body of the Ministry of Social Affairs and Employment charged with criminal investigations - had been given the go-ahead to raid the farm on Friday because the sleeping quarters were in breach of fire regulations. It was then that the extent of the conditions came to light.

The 50 farmhands, many of them Romanian, were not allowed to leave the premises and were sleeping in a filthy room without a window. The workers were being paid less than the agreed wage.

The farm owner has already been fined five times by the labour inspectorate since 2005 for employing illegal immigrants, paying under the minimum wage and failure to report an on-site accident. The fines amounted to more than 500,000 euros.