I have recently spent a great deal of money setting up raised beds to allow me to begin growing my own vegetables, something I have always wanted to do but never had the chance. However, having got everything ready including seeds etc I have been told that I cannot use the beds because there are old Railway sleepers below them, which have very likely seeped oil and other nasties into the ground.

Obviously I don't want to end up growing veg that will make us sick, so I need to know if this really does mean that these beds are only good for flowers etc or whether I have any chance of growing veg safely there?

(I bought the house with the sleepers in place so they have been there for anything from 5 to 10 years.)