The Army Criminal Investigation Command announced this week that it hasn't been able to determine what has caused the deaths of 10 infants at Fort Bragg, N.C. since 2007. According to medical examiners the deaths were due to "undetermined" causes. The investigators found no evidence that the deaths were related to any exposure to environmental contamination or to any type of criminal activity.

The announcement doesn't include details about the methods used to reach that conclusion.

CID began its investigation after three infants died in the same home between 2007 and 2009. After an eighth child died on base in 2009, CID began to suspect that sulfur gasses from the drywall used in the homes could have something to do with the deaths.

Early tests commissioned by CID showed that the drywall was indeed problematic, but later tests done using a different method showed the drywall was fine. CID also tested the homes for pesticides, but announced in March that the levels weren't high enough to cause health problems.

The Consumer Product Safety Commission, the lead agency in the federal government's two-year investigation of tainted drywall, has also examined the infant deaths and ruled out environmental causes. Testing done by the CPSC on Ft. Bragg came under fire from drywall experts, who said that more advanced testing methods should have been used.

At a Senate Armed Services Committee hearing in March, Army Secretary John McHugh said he had assigned a team from the Army's Public Health Command to pursue its own study of the infant deaths. That study is still underway, according to a spokesperson for Ft. Bragg.

Two more deaths have occurred since the investigation began, bringing the current tally to 12. The most recent deaths are still being investigated.