An earlier draft of the script was about giant killer leeches. This was later changed to zombies when Fred Olen Ray realized that leech costumes would be too expensive for the film's modest budget.
The opening scene with the reporter was added to the movie at the last minute in order to pad the film's running time to a reasonable feature length.
According to Fred Olen Ray, casting Buster Crabbe to play the sheriff made a big difference to the local authorities in the small town they filmed in outside of Orlando, Florida. They gave Ray and his team access to police cars and uniforms, and gave them authority to shoot anywhere they wanted.
Paul Blaisdell offered to do the special effect of the meteor falling down from the sky, but ultimately was turned down because he wanted to be paid a thousand dollars for the effect.