In this task, a passage will be given and the goal is to generate a question about temporal relations based on that passage. A temporal relation describes the relation between two things with respect to time e.g., something happens/starts/terminates/... immediately/shortly/usually/... before/after/during/... something else.
Your question should include an event, or ask about an event, and should not be a yes/no question.
Q: Passage: German police subsequently found traces of the polonium in Hamburg, where one of the contacts, Dmitry Kovtun, stopped on his way from Moscow to London for the meeting. Hamburg prosecutors have opened a criminal investigation against Kovtun for apparently bringing the radioactive substance into the country from Russia and said they considered him "more a perpetrator than a victim."
A:
What event has already finished?