An investigation into a meat scandal expanded nationwide as China's top food quality watchdog launched a "thorough" probe on Monday.

China Food and Drug Administration asked local authorities to investigate all the food factories invested by US food supplier OSI Group in provinces of Hebei, Shandong, Henan, Guangdong and Yunnan.

The administration will scrutinize meat sources and the process of food production in these factories. Law or regulation violators will face severe punishment.

Local TV aired a news program on Sunday alleging that Shanghai Husi Food Co, Ltd, a unit of OSI Group, had supplied products tainted with reprocessed stale meat to a string of fast food chains and restaurants across China.

Law enforcement officials have suspended production at a suburban plant of Shanghai Husi Food Co, and further investigation is underway.