"gzip: stdin: invalid compressed data--format violated" error when extracting a tgz archive

I have to open a tar file. I used the following command line on my Unix shell: tar xfvz raw-GWA-data.tgz I found the following error message: gzip: stdin: invalid compressed data--format violated tar: Child returned status 1 tar: Error is not recoverable: exiting now Then, I tried the following command lines: tar -xvzf raw-GWA-data.tgz tar --extract --file raw-GWA-data.tgz tar xzf raw-GWA-data.tgz tar -xf raw-GWA-data.tgz and I found the same error without the possibility of opening my tar file. What's wrong? There're alternative ways to open my tar file?