U.S. military authorities have conceded that fuel oil has leaked out of U.S. forces' main unit in central Seoul.
A spokesman for the Yongsan base said a U.S. military investigation team has discovered traces of oil in at least two of the 22 soil samples taken beneath the Yongsan base.
Lieutenant Colonel Daniel Worth, the garrison's facility engineer commander, said the findings could mean the leaks have been occurring over some time.
It is the first time that the USFK has conceded that heating fuel from its tanks had leaked into the ground under the base.
Worth, however, denied that the latest findings have any relation to the discovery of oil in manholes at a nearby subway station.
Korean officials and environmental groups have raised suspicions that the entire area near the U.S. military base in central Seoul could be seriously contaminated.
Meanwhile, Green Korea United, a civic environmental group, called for the U.S. army to take punitive actions against those responsible for the leakage and to offer an apology to the Korean people.