Cannot load library QVTKWidgetPlugin.dll: Unknown error 0x000000c1

I am having a problem to integrate QVTKWidgetPlugin into Qt. I have compiled VTK with MSVC 2014 x64 with settings below

VTK_Group_Qt ON
VTK_QT_VERSION 5
VTK_BUILD_QT_DESIGNER_PLUGIN ON
Module_vtkGUISupportQtOpenGL ON
Module_vtkGUISupportQt ON
Module_vtkRenderingQt ON
Module_vtkViewsQt ON

I have copied QVTKWidgetPlugin.dll to C:\Qt\Tools\QtCreator\bin\plugins\designer but there is no widget is shown on tool menu. When I checked Tools>Form Editor>About Qt Designer Plugins I see QVTTKWidgetPlugin could not be loaded with message below: "Cannot load library C:\Qt\Tools\QtCreator\bin\plugins\designer\QVTKWidgetPlugin.dll: Unknown error 0x000000c1"

I have set environment variable to QT_DEBUG_PLUGINS=1 and then started a sample app but there is no output related with QVTKWidgetPlugin.

How can I get the reason of the problem?

Thanks