NEW YORK CITY — Twenty-one people in the New York City region were arrested on Wednesday and charged with cheating on their commercial driver license (CDL) written examinations.

The new development is part of New York State Inspector General Catherine Leahy Scott’s ongoing investigation into a CDL test cheating scheme first revealed in September of last year.

“People with commercial driver licenses operate school buses and heavy-trailered vehicles that carry hazardous chemicals and petroleum,” Scott said. “We entrust the operators of these vehicles to safely bring our children to and from school. We count on them to navigate very busy transportation networks without getting into catastrophic accidents. Test cheating puts innocent people at grave risk and cannot be tolerated."

Manhattan District Attorney Cyrus Vance Jr. said that the 21 defendants "are accused of fraudulently obtaining specialized licenses, putting at risk the lives of everyone who shares our roadways.”

Last September, Scott, Vance and U.S. Attorney Loretta E. Lynch announced the arrest of eight ringleaders, eight test takers and three security guards for their alleged roles in the scheme.

In the scheme, test takers agreed to pay ringleaders to secure the correct answers for the tests. Test takers would leave the testing area and hand their blank test to a scheme organizer or an associate, who would then take the blank test to a person with knowledge of the answers.

The completed test was then returned to the test takers for submission to a Department of Motor Vehicles clerk. The inspector general found that the scheme was facilitated by allegedly bribing security guards.

The 21 people arrested on Wednesday are accused of engaging in the same scheme.

CDL applicants take a core examination and then supplemental endorsement tests for specified areas, such as hazardous material transportation, school bus driving or the operation of tandem trailer trucks and tow trucks.

"When your child gets on the school bus in the morning, you should not have to worry that the bus driver obtained a commercial driver’s license through a fraudulent scheme," said James Hayes Jr., special agent in charge of Homeland Security Investigations New York. "Today’s arrests remove dangerous drivers from our streets and make our roads and our communities safer.”