"can't find DLL error" for DLL dependency of plugin DLL

I am trying to call functions from a DLL (mlpack.dll) that itself depends on another pair of precompiled DLLs, but whenever I attempt to load mlpack.dll using FPlatformProcess::GetDllHandle I receive a “System Error” message saying that a dependency DLL (blas_lib64_MT) is missing from the computer. I have set the system PATH and Path variables (OS is Win 7) to include the dependency DLL location but this does not fix the issue. I also tried to manually load the dependency DLLs by including them in a Plugins directory similar to:

but this also results in the same error. Any ideas on how to fix this?

Also: I compiled mlpack.dll as a separate Visual Studio project outside of the UE4 project. Could that cause this issue? Thanks.

It appears that placing the dependencies in System32 at least allows for the engine to load the DLL correctly. It would still be nice to have a more elegant solution for distribution, though.

Easy,solution is to put the DLL near to you binaries,and everything will works fine.
But when you loading the dll?Does the Path to dll is correct?check it.

Also: I compiled mlpack.dll as a separate Visual Studio project outside of the UE4 project. Could that cause this issue? Thanks.

Answer : No,but it should be x64 dll.