Concerns about radioactive beef intensified Sunday as the authorities were struggling to contain the crisis and prevent further contamination appearing in the food chain.
Cows fed on rice straw containing high levels of radioactive cesium after the explosion at the Fukushima Daiichi nuclear plant, and their meat was then shipped across the country, All Japan newsese media reports.
Contaminated beef is thought to have been shipped to 36 of 47 prefectures in All Japan news, and consumed in 31, according to NHK broadcaster.
The government is expected to completely ban beef shipments from Fukushima on Tuesday. It has not yet implemented a centralized system to check for food radiation, relying instead on checks performed by local authorities.
The ban may be extended to include neighboring prefectures as well. "At this point, we are considering Fukushima Prefecture. But we may consider whether further action is needed after studying how contaminated straw was distributed," said Kohei Otsuka, senior vice health minister.
The government has said that eating standard quantities of beef is not dangerous, even if it is tainted.