MEXICO CITY (Reuters) - A laboratory in Mexico City suspected of producing the powerful opioid fentanyl was raided on Wednesday, officials said, in a rare case of a bust involving a drug that is increasingly blamed for fueling the opioid crisis in the United States.

More than 72,000 Americans died from drug overdoses last year, including illicit drugs and prescription opioids. U.S. President Donald Trump declared the opioid addiction crisis a public health emergency.

Fentanyl is the most lethal type of opioid used in the United States, according to the Drug Enforcement Administration (DEA), and gained notoriety after an overdose of the painkiller was deemed to have killed pop singer Prince in 2016.

The drug is trafficked into the United States largely from China and Mexico but it is not currently possible to determine which country is a bigger supplier, the DEA said in a report in October.

Investigations led to the discovery of the lab in the northwest of Mexico City, the attorney general’s office in the Mexican capital said in a statement.

Officers in white protective jumpsuits raided the site at night and found small blue pills and large plastic jugs containing dark liquid, images from the prosecutor’s office showed.

Their finds also included chemical substances, machinery and supplies likely to be used to fabricate fentanyl, it said.