Several things that you might want to explain further:

1. How does asking for OP [and his client's] telegram details fit into this investigation of the source of fund?

2. Why do OP has to be [initially] the one asking his client to provide details and how is it not counterproductive toward an investigation of the legality of fund like what I pointed out here?

3. How is what he provided from his side is not enough? He proves that he worked for it, got them as a payment. Unless proven otherwise, it's all legal from his side in a sense that he's not involved or have any idea in the said criminal activity.

4. How do you think OP will know that the fund is related to criminal activity instead of being a pure innocent here? Wouldn't considering him ineligible to prove the source of fund as he's not the sender rather contradict the assumption that he's being involved in the activity [which become the reason why you hold his fund, because he knows it's tainted, otherwise, he's clueless, innocent, and the fund should be released to him]?

5. How much from that fund is marked as tainted? All of it?