CHICAGO, May 5 (Reuters) - Tyson Foods ( TSN ) has been

"proactively reformulating" products containing petroleum-based

synthetic dyes and will finish work to eliminate them from its

production process by the end of May, CEO Donnie King said on

Monday.

Most of the meat company's retail-branded products,

including Tyson chicken nuggets, do not contain those types of

dyes, King said on an earnings call.