This article is by David Jolly, Hiroko Tabuchi and Keith Bradsher.

TOKYO — Japan’s troubled effort to contain the nuclear contamination crisis at its stricken Fukushima Daiichi plant suffered a setback on Sunday when alarmingly high radiation levels were discovered in a flooded area inside the complex, raising new questions about how and when recovery workers could resume their tasks.

Tokyo Electric Power Company, the operator, said the elevated radiation levels in the water, which had flooded the turbine buildings adjacent to the reactors at the plant, were at least four times the permissible exposure levels for workers at the plant and 100,000 times more than water ordinarily found at a nuclear facility.

That could mean crews seeking to determine damage and fix the problems at the plant, hit by a magnitude 9.0 earthquake and a tsunami more than two weeks ago, may not be able to approach some of the most troubled parts of the complex until the water can be safely removed.

Tetsuo Iguchi, a professor in the department of quantum engineering at Nagoya University, said that at the sharply elevated levels of radiation, workers would be able to remain on the site for only about 15 minutes before health considerations required them to leave. That could compromise attempts to bring the crisis under control.