MIAMI (AP) — Republicans on the House Oversight Committee have launched an investigation into a controversial policing tactic that permitted staggering amounts of deadly fentanyl to reach the streets as federal authorities sought to build bigger drug cases.

The committee’s chairman, Rep. James Comer, a Republican from Kentucky, sent a letter Monday to Attorney General Todd Blanche requesting records related to the U.S. Drug Enforcement Administration’s controversial strategy of monitoring — yet not seizing — major fentanyl shipments.