There is currently no publicly available information to suggest that Silvergate Bank is under investigation by the U.S. Department of Justice over its involvement in the collapse of FTX, which is a cryptocurrency derivatives exchange.
It is possible that this information may emerge in the future, but at this time there is no evidence to support the claim that Silvergate Bank is under investigation for this reason.
That being said, Silvergate Bank is known for being a key player in the digital currency industry, and it has established partnerships with a number of prominent cryptocurrency companies. Given the evolving regulatory landscape and the increasing scrutiny of the cryptocurrency industry by government agencies, it is possible that Silvergate Bank could face investigations or other regulatory challenges in the future.
However, it is important to note that this is speculative at this point, and any specific investigations or regulatory actions would depend on a variety of factors and would need to be confirmed by official sources.