The Justice Department is investigating whether multiple airlines joined forces and colluded by limiting available seats, allowing them to raise prices, the Associated Press reported Wednesday.

A spokeswoman from the Justice Department confirmed to the news service that the agency is investigating "unlawful coordination" among major airlines, but did not say which airlines are being probed.

The investigation is focused on whether the carriers colluded illegally and informed each other as to "how quickly they would add new flights, routes and extra seats," the AP reported.

Such collusion could be responsible for rising airfares, which increased by 13 percent from 2009-14, according to the Bureau of Transportation Statistics.

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