The European Commission said on Friday it had opened an in-depth investigation into alleged state aid to two container terminal operators in Europe's second busiest port, Antwerp in Belgium. The Commission said concession agreements for PSA Antwerp NV and Antwerp Gateway NV contained a requirement for the handling of a minimum tonnage. The two did not reach this between 2009 and 2012, meaning they would have to pay compensation to the publicly-owned port authority. However, the Antwerp Port Authority decided in 2013 to reduce the minimum tonnage retroactively, reducing the compensation to be paid by some 80 percent. The Commission said…