Story highlights A former co-owner of a California slaughterhouse is accused of distributing bad meat

The other co-owner and two former workers are also facing charges in the case

Prosecutors: Robert Singleton was responsible for buying cows and loading shipments

Authorities recalled nearly 9 million pounds of meat from the slaughterhouse in February

A second former co-owner of the California slaughterhouse involved in a recall of nearly nine million pounds of meat was charged with knowingly processing and distributing meat from cancerous cows, court documents released this week say.

Robert Singleton, co-owner of the Rancho Feeding Corporation in Petaluma, was primarily responsible for purchasing cattle and loading shipments for distribution, prosecutors say.

He is charged with distributing "adulterated, misbranded, and uninspected" meat, according to the documents.

Singleton jointly owned the meat plant with Jesse J. Amaral Jr., the former president and general manager who is also known as also known as "Babe Amaral."

Amaral and his former employees, Felix Sandoval Cabrera and Eugene Corda, have all been charged with unlawful sale and distribution of contaminated meat.

Prosecutors allege that Amaral and Singleton directed Corda and Cabrera to circumvent inspection procedures for certain cows with signs of epithelioma of the eye, also known as "cancer eye."

While Singleton is accused of knowingly purchasing cattle with signs of epithelioma, Amaral allegedly directed employees to carve "USDA Condemned" stamps out of certain cow carcasses and to process them for sale and distribution, despite having been rejected by the U.S. Department of Agriculture veterinarian.

Amaral is also charged with sending false invoices to farmers, telling them that their cattle had died or been condemned and charging them "handling fees" for disposal of the carcasses, instead of compensating them for the sale price, prosecutors said.

If convicted, Singleton faces up to three years imprisonment, with one year of supervised release, and a $10,000 fine. Amaral, Cabrera and Corda could receive up to 20 years in prison and $250,000 in fines.

CNN's attempts this week to reach the four men and an attorney representing them have been unsuccessful.

Between January 2013 and January 2014, Rancho processed and distributed meat from approximately 101 condemned cattle and approximately 79 cancer eye cows, according to court documents.