The German government has expressed deep concern over the downing of a Turkish military plane inside Syrian territorial waters yesterday and called for detailed investigation into the incident which the Syrian government confirmed that it took place. German foreign ministry sources quoted federal foreign minister as saying ''we are deeply concerned over the downing of the plane and we call for preventing the Syrian crisis to plug into more escalation''. Syria said the Turkish fighter jet was flying low, well inside Syrian territorial waters when it was shot down. Syria shot down a Turkish warplane over the Mediterranean on Friday and Ankara warned it would respond decisively to the incident that threatened to open a new international dimension in the 16-month revolt against Syrian President Bashar Assad.