The New York Times,TOKYO — Despite continuing fears over the safety of food from the area of the disaster-stricken Fukushima Daiichi nuclear power plant, Japan has lifted a ban on beef shipments from there that it had imposed just a month ago, when meat contaminated with radioactive material was found to have reached Japanese supermarkets.

The decision to lift the ban underscores the difficulty faced by the government. Officials are eager to minimize the harm to farmers from the Fukushima area and to bring the local economy back to normal, but they are also trying to repair the damage to their credibility from the handling of the nuclear disaster, caused by an earthquake and tsunami in March.

The discovery of radioactive cesium in a number of products last month has greatly undermined public trust in the safety of produce from the region, even if, as the government says, the amount that was found was tiny.

“There is no safe level of internal radiation exposure, especially for children,” Tatsuhiko Kodama, head of the Radioisotope Center at Tokyo University, said in an interview this month.

Inside the 12-mile evacuation zone around the nuclear plant, where three reactors melted down, all farming has been abandoned. But radiation that exceeds safety levels has been detected in tea, milk, fish, beef and other foods produced outside that zone, and as far as 200 miles from the plant. Officials in Fukushima and in neighboring prefectures sporadically check a range of products but do not have the capacity to screen all of the region’s farm produce for radiation.

The government imposed the ban on beef from Fukushima and three neighboring prefectures in July only after radioactive cesium was found in samples of meat from the region. Local officials traced it to straw fed to the cattle that had been stored outdoors, and suggested that rain might have brought the contamination.

Adding to concerns, basic radiation checks with handheld dosimeters failed to detect the ingested cesium in the cattle.

More than 1,000 cows are thought to have been shipped to market after being fed radioactive straw, and the contaminated meat has been tracked to supermarkets and school lunchrooms across the country. Radioactive cesium decays very slowly, with a half-life of 30 years. Spread through the human body, it can increase the likelihood of cancer.

The government has instructed farmers to stop feeding cows hay that could be contaminated, and all meat from farms known to have had contaminated hay will undergo laboratory tests before it can be shipped, agriculture officials said. Other farms will have to have meat from at least one cow tested before shipping.

“We have established safety control measures in each prefecture through monitoring feed and testing,” Yukio Edano, the chief cabinet secretary, said at a news conference.

He said Thursday that the government was lifting the ban for Fukushima, Iwate and Tochigi Prefectures in eastern Japan, after lifting a similar ban on Miyagi Prefecture last week. The step was delayed six days by the discovery that a Fukushima farmer had shipped more contaminated beef.