Updated

U.S. taxpayer money meant to cover transportation costs in Afghanistan reportedly has made its way into Taliban hands after trickling through a series of subcontractors.

The funding was traced as part of a year-long military investigation. The Washington Post reported the probe found "documented, credible evidence" that four of the eight main trucking companies paid under a $2.16 billion U.S. contract were either involved in "a criminal enterprise or support for the enemy."

The money traveled through several bank accounts before winding up, in some cases, across enemy lines. In one instance, investigators reportedly traced a $7.4 million payment as it was distributed to several subcontractors which then deposited money into the account of the Afghan police commander in exchange for safe passage. From there, the Post reported, officials saw $3.3 million move from that account to insurgents in the form of weapons and cash.

The Post reported that all eight companies that were examined are still on the U.S. payroll. The findings follow prior allegations that U.S. money was inadvertently supporting a protection scheme that benefited insurgents.

A senior U.S. official told the Post that the a new system for trucking contracts will soon be announced, bringing more trucking firms into the system and requiring more information about subcontractors.

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Asked for comment, Pentagon spokesman Col. Dave Lapan suggested the findings of the report were overblown. Lapan said the investigation was ordered by Gen. David Petraeus and showed some undetermined amount of money made its way to the insurgency due to corruption with the contract.

"Record-keeping problems and difficulty following money from contractor to subcontractor led to the fraud," Lapan said.

Click here to read the full story in The Washington Post.