Before buying land, get lawyer to do due diligence

We are a chama of five and resolved in our last two meetings to buy land on the outskirts of Nairobi. We intend to subdivide the land among ourselves for private ownership. However, we are concerned about cases of government institutions claiming ownership of properties that have been bought through legal procedures. What can we do to ensure no one later comes to lay claim on the land we are planning to buy? Is there any legal requirement to be undertaken before purchasing land from a parastatal or state corporation to avoid instances where the transaction is revoked?

Rebecca, Nairobi.