(Photo Credit: Manpreet Romana/AFP/Getty Images)

Millions of dollars that were supposed to be spent protecting American troops from deadly improvised explosive device (IED) blasts on Afghan roads were squandered by government contractors whose inaction may have cost lives, according to a new inspector general report.

Roughly $32 million was supposed to pay for so-called "culvert denial systems," which are essentially steel grates installed to block access to the drainage culverts that run beneath Afghan roadways. Insurgents had been using the culverts to hide explosives.

"Contractors either had failed to properly install culvert denial systems, rendering those systems ineffective and susceptible to compromise by insurgents, or did not install them at all," according to the report by Special Inspector General for Afghanistan Reconstruction, which was made public Tuesday morning.

"Our preliminary investigation found that at least two Afghan contractors-with a total contract amount of nearly $1 million-in one Afghanistan province have committed fraud by billing the U.S. government for the installation of 250 culvert denial systems that were either never installed or incorrectly installed," the report says.

DOWNLOAD: SIGAR Report on Afghan IED Protection

The report says the inspector general's office is continuing its investigation, and that one goal is to determine whether the failure by any contractors to perform the work may have been a factor in the death or injury of American troops.

Already, the report says, one Afghan contractor and his sub-contractor have been arrested and charged with fraud and negligent homicide.

Investigators appear to have had a great deal of difficulty determine just how many of the drainage covers were supposed to be installed, and of those, how many actually were put in place. In part, the report says, that is because the contracts were handed out by a variety of different military commands inside Afghanistan. The inspectors were able to find contacts for at least 2,500 installations, but found hundreds of those were never actually completed.

Col. Jane Crichton, a military spokeswoman in Afghanistan, told The New York Times that military commanders in Afghanistan have introduced quality assurance experts and policy guidelines to better oversee projects. She told the paper, which first reported on the inspector general's findings, that commanders were also trying to locate the grates and ensure they were working.