He was awarded a new contract for the 2010 season.
The contract will be awarded for a period of one year.
Now, the focus will be on how such a contract could have been awarded in the first place.
A second contract for the same amount was awarded 10 days later, the department said.
That contract was awarded by officials who had no idea the son even worked for the company.
At the end of the 2006 season, Thomas was awarded a new contract.
In total, 19 contracts were awarded between 1973 and 1976.
The original £200m contract was awarded on 3 May 2007.
By the end of the year, all contracts were awarded.
The state is expected to decide in about a week which company will be awarded the contract.