old sitemap files

When I first ran the sitemap generator, I hadn't restricted the types of files I wanted included. Now I'm only using up to sitemap_1.xml.gz. But my directory still has the old files up to sitemap_19.xml.gz. Yahoo is only using the new file but google is still using all 19 files.
I'm not sure why google is ignoring my new sitemap.
Is it all right to just delete the old files about sitemap_2.xml.gz?
thanks

You should remove all *.gz files from data/ folder and regenerate sitemap.

thanks