Reliable information in this regard is available from Altlastenkataster or Verdachtsflächenkataster registries. If your property is listed in such a register, it will also contain initial indications as to the type of use involved. The relevant authorities are required by law to provide you with such information, if you are the owner of the property in question or are interested in purchasing it.

Apart from this, you can also ask neighbors or residents if they have any information about how the property was used in the past. If your initial suspicions that your property is contaminated are confirmed, you can hire an expert to investigate the matter further.