A U.S. military contractor was killed Monday and three others injured in an accident that may have involved unexploded ordnance at the largest American military base in Kuwait, the U.S. military said.

The military did not identify the workers or give their nationalities but said in a statement that initial reports indicated the accident at Camp Arifjan involved workers who "may have disturbed unexploded ordnance."

No Americans or Kuwaitis were among the dead and injured, the military said. Some of the base's contract workers are from Asian countries.

The military was withholding the names of the dead and injured pending notification of their families, and the accident was under investigation. The three injured were taken to the base hospital for treatment, the U.S. military statement said.

This small oil-rich state has been a major ally of Washington since the U.S.-led 1991 Gulf War that liberated it from a seven-month Iraqi occupation under Saddam Hussein. It was the launching pad for the 2003 invasion of Iraq and remains a logistics base for coalition forces serving there.