Multiple GPU card recognization error in Ubuntu 14.04 with CUDA 6

I am trying to make Ubuntu 14.04 LTS (32 bit version) working with CUDA 6.
I have successfully installed CUDA toolkit, Recent NVIDIA driver on the system. The problem is when I run the deviceQuery it does not show the expected results.

I tried with nvidia-smi -L
It shows only 2 GPU, where I have 4 GPU in the mother board (GPUs are of type Geforce GTX 590 each of which contains two GPU in a single assembly). In my case with the above mentioned command It shows two GPUs with their corresponding IDs and addresses, but for other two GPUs it shows two messages saying " unable to determine the type of the device connected"

I tried reboot, re-installing CUDA as well as NVIDIA driver but no luck.

If any of you have experience with this kind of problem please share you experiences.

Any suggestion/help is highly appreciated.
Thanks a lot.