(NAFB) – Meat processor JBS says China blocked shipments from the company’s Colorado plant because traces of ractopamine, a feed additive, were found in beef headed to China.

The Poultry Site says Brazil-based JBS, the world’s biggest meat processor, announced in a statement that it’s working with U.S. and Chinese authorities to resolve the situation. No other JBS beef facilities in the U.S. have been impacted by the Chinese announcement.

Ractopamine is a feed additive used to boost animal weight. At least 160 countries, including the EU, Russia, and China, have banned or restricted the supplement’s use. Earlier this year, food safety, environmental, and animal rights groups filed a lawsuit against the Food and Drug Administration seeking to force it to reconsider approvals of ractopamine.

The groups say the additive is putting human health at risk and causing greater stress in farm animals before slaughter. USDA officials had no immediate comment.