Any valuables found on a Nazi train buried in Poland since World War Two must be returned to their rightful owners, the World Jewish Congress said on Friday."To the extent that any items now being discovered in Poland may have been stolen from Jews before they were sent to death ... it is essential that every measure is taken to return the property to its rightful owners or to their heirs," WJC head Robert Singer said in a statement issued in New York."We very much hope that the Polish authorities will take the appropriate action in that respect." Polish officials said on Friday they were almost certain they had located the train.