Inspectors have located the contaminated area of a nuclear waste repository in the southern U.S. state of New Mexico, which has been shut down for more than two months due to a radiation leak. The discovery was made during the fourth visit by inspectors into the Waste Isolation Pilot Plant, an underground dump located near Carlsbad in southeastern New Mexico, local TV KOB quoted energy department officials as saying Friday. Tammy Reynolds, deputy recovery manager of the U.S. Department of Energy, told media that on Wednesday inspectors detected elevated radiation levels as they approached a panel used to store nuclear waste. The inspectors had to retreat before pinpointing the exact source of contamination because they had been underground for five hours in protective gear and the batteries on their respiratory equipment were running low, Reynolds said. They are expected to make more trips into the dump next week to find out what caused the leak and the extent of the contamination. U.S. officials said earlier that they could possibly deploy robots to inspect the area if it is unsafe for humans to continue the recovery work. The radiation leak occurred on Feb. 14 and contaminated 21 workers, though their levels of exposure were said to be "extremely low" and well below those deemed unsafe. The prolonged closure of the repository has forced Los Alamos National Laboratory, a nuclear weapons manufacturing facility in New Mexico which used to store its refuse at the plant, to relocate its radioactive waste to Texas. The cause of the radiation leak still remains unknown. A truck fire was reported at the underground site nine days before the leak and prompted evacuations, but officials said the fire was in a different part of the site and did not seem related. The repository stores "transuranic waste" leftover from nuclear weapons research and testing from the nation's past defense activities, according to the website of the energy department. The waste includes clothing, tools, rags and other debris contaminated with radioactive elements, largely plutonium.