JAPAN has found radiation above the legal limit in beef from near a stricken nuclear plant, the first such finding in meat since a quake and tsunami triggered the atomic crisis, local media reports.

The health ministry said 510 becquerels of radioactive cesium had been detected in beef from Tenei in Fukushima prefecture, about 70km from the plant - exceeding the 500-becquerel limit, Kyodo News said.

But further checks are being carried out on beef from the region, an official from the Nuclear and Industrial Safety Agency was quoted as saying, because of a gap in radiation levels between the Tenei sample and others.

The government has already halted shipments of untreated milk and many vegetables from Fukushima and three neighbouring prefectures after radioactive substances were found in samples of the foodstuffs.

It has stepped up radiation monitoring in another six prefectures, covering an area that borders Tokyo.

On Saturday, officials said that lettuce contaminated with radiation above the legal limit had been found at a wholesale market in central Japan, shipped from a farm north of Tokyo.

The twin natural disasters on March 11 severely damaged the Fukushima nuclear plant, which is leaking harmful radioactivity that has also prompted the evacuation of local residents.