(Jonathan Ernst/Reuters)

Seven U.S. senators sharply criticized the Drug Enforcement Administration this week for failing to answer questions about enforcement actions against pharmaceutical companies accused of violating laws designed to prevent painkillers from reaching the black market.

“We received an insufficient response that ignored those questions almost entirely and recited boilerplate information about the DEA’s mission,” said the letter to the acting DEA administrator, Chuck Rosenberg.

The DEA did not respond to a request for comment.

The senators sent the questions in October after The Washington Post reported that the agency had slowed its enforcement efforts in the face of the opioid epidemic, which has taken nearly 180,000 lives since 2000.

The Post reported that starting in 2013, DEA lawyers at the agency’s headquarters delayed and blocked enforcement efforts against large opioid distributors and others, requiring investigators to meet a higher burden of proof before they could take action.

Five former supervisors from the agency’s Diversion Control Division told The Post in on-the-record interviews that they had become increasingly frustrated by the sharp drop in enforcement actions. They said their civil cases were suddenly being subjected to a higher standard of proof, similar to that required in criminal cases.

The supervisors’ concerns were confirmed by reports filed by the DEA’s chief administrative law judge, who found that the number of cases approved at headquarters was “stunningly low for a national program.”

On Dec. 2, DEA officials held an off-the-record briefing for the senators. But the lawmakers said in the letter sent Wednesday that the session was not a “substitute for written responses to our questions.”

The senators said they wanted to know whether civil filings had fallen and if so, why. They also asked whether the Department of Justice played a role in policy changes that have affected enforcement.

“Since we wrote to you, the Centers for Disease Control and Prevention (CDC) has released new data showing that the U.S. opioid epidemic is growing and that prescription and illicit opioids remain a driving force,” the senators wrote. “Especially in light of this new data, Congress and the American people deserve an explanation of how the DEA is enforcing laws that could help address this public crisis.”

The letter was signed by Democratic Sens. Edward J. Markey (Mass.), Richard J. Durbin (Ill.), Joe Manchin III (W.Va.), Amy Klobuchar (Minn.), Tammy Baldwin (Wis.) and Richard Blumenthal (Conn.), as well as independent Bernie Sanders (Vt.).

Sens. Patrick J. Leahy (D-Vt.) and Ron Wyden (D-Ore.) sent a similar letter to Rosenberg and U.S. Attorney General Loretta E. Lynch after the Post stories. Wyden said Wednesday that the response was “totally inadequate given the life-and-death nature of the opioid crisis.”