ST. LOUIS–State conservation experts are still trying to figure out why dozens of crows have died recently in the area around the Thomas Eagleton federal courthouse in downtown St. Louis, but they have been able to rule out at least one potential cause.

Dan Zarlenga, a spokesman for the Missouri Department of Conservation told FOX2 Friday that preliminary testing did not find avian influenza in any of the birds submitted so far. More testing is still being done to determine the cause.

The department’s own physical exams of the birds found no signs of wounds.

Bird flu cases have been discovered in turkeys as close as Kentucky and Indiana.

In the meantime, sonic bird deterrents, which mimic the sound of birds in distress, have been installed near the courthouse in hopes of scaring off other birds.