Updated

New York state officials say they suspect test takers cheated on hundreds of tests to operate the most vulnerable vehicles on the road — from trucks hauling hazardous materials to school buses — and eight commercial drivers have been charged so far.

Nineteen suspects, including three security guards, were arraigned and pleaded not guilty to charges linked to what officials say is an elaborate scheme to obtain commercial driver's licenses with purchased test replies.

State Inspector General Catherine Leahy Scott said Thursday the arrests represent the tip of the iceberg, but investigators don't yet know exactly how many drivers might be on the road with criminally obtained licenses.

The investigation was first reported by the New York Daily News.