WASHINGTON — The Justice Department is investigating claims that major drug and medical device companies doing business in Iraq knew that the free medicines and supplies they gave the government to win business there would be used to underwrite terrorist attacks on American troops.

In a regulatory filing last week, AstraZeneca, a drugmaker based in Britain, disclosed that it had “received an inquiry from the U.S. Department of Justice in connection with an anti-corruption investigation relating to activities in Iraq.”

The filing said the inquiry was related to a lawsuit filed last year in federal court that accused five companies of winning contracts to sell their products to the Iraqi Ministry of Health with the understanding that they also provide additional medical supplies and medicines for free. The five companies are General Electric, Johnson & Johnson, Pfizer, Roche Holding A.G. and AstraZeneca.

The lawsuit was filed on behalf of members of the American military who were injured or killed in attacks from 2005 to 2009, at the height of the Iraq war.