Lawmakers are targeting a deadly development in the battle over opioid abuse: powerful synthetic opioids that are trafficked in to the U.S.

A bipartisan bill introduced Tuesday in both the Senate and House aims to stop the trafficking of synthetic drugs such as fentanyl, which are 50 times more potent than heroin. The Synthetics Trafficking & Overdose Prevention Act aims to target weaknesses in the international mail system that enables the drugs to get into the U.S. from overseas.