The sacking followed an embassy investigation after staff noticed a person wandering around the premises "in a state of confusion and appearing to be intoxicated", the Wall Street Journal reported earlier this week.
"We can confirm that six individuals were involved and that all of them were contract employees," the US State Department told AFP late yesterday.
"No State Department employees were involved in the incident."
It was not immediately clear what kind of drugs the employees were using.
Opium production is a major source of income for the Taliban insurgents.
Last year, Afghanistan saw a 10 per cent jump in opium cultivation compared to the previous year because of bumper harvests, collapsing eradication efforts and declining international aid to combat drugs, according to the United Nations.
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