Image caption Retailers have already bought contaminated beef from Fukushima

The Japanese government has banned all shipments of cattle from the Fukushima prefecture on concerns about contaminated beef.

More than 500 cows are thought to have eaten radiation-tainted hay and already been shipped to other parts of Japan.

There are also concerns that beef from other surrounding prefectures may be contaminated.

This is the latest health scare linked to the Fukushima Daiichi nuclear power plant damaged by March's earthquake.

"We instructed the governor [of Fukushima] to halt shipments of all cattle in Fukushima to meat-packing factories," said chief government spokesman Yukio Edano.

Wider problem

The initial discovery of contaminated beef was traced back to farms near the Fukushima power plant, but more recent discoveries are from farms as far as 100km (70 miles) away.

However, farm ministry officials have said that consuming the beef a few times would not pose a health risk, despite radiation levels several times the national limit.

Shipments of certain vegetables from areas near the plant had already been halted due to high radiation levels.

More than four months on from the earthquake, radioactive material continues to escape from the facility.