UPDATE: This article has been updated to include more information from the U.S. Attorney's Office, including details about Rodas and his plea agreement.

CUMBERLAND, RI — Federal drug enforcement authorities have arrested a Cumberland man and seized 660,500 fake adderall pills in what U.S. Attorney for Rhode Island Zachary Cunha called the "single largest seizure" of its kind in the U.S.

Dylan Rodas, 27, has agreed to plead guilty to possession with intent to distribute 500 grams or more of methamphetamine in connection to the massive bust that took place in late March, officials said.

Speaking at a press conference in Providence on Monday morning, officials said the drugs seized by federal drug enforcement agents are worth an estimated $4.6 million.

Also found in the search were two pill presses capable of pressing more than 5,000 pills per hour, as part of what authorities called an "industrial-scale" drug-making operation.

Officials said the meth came from Mexico.

"The quantity of methamphetamine represented by this seizure — methamphetamine that was packaged and ready to flow out onto the street, to devastating effect in our communities — is staggering," Cunha said.

According to Cunha, the pills weighed a total of 660lbs — "roughly the weight of a V8 car engine or a baby grand piano," he added.

Other drugs seized during the investigation include seven kilograms of methamphetamine powder yet to be pressed into pills, as well as fentanyl and crack cocaine.

Authorities also seized $15,000 in cash and seven handguns.

The firearms included two ghost guns and two guns with defaced serial numbers, officials said.

"DEA is committed to investigating individuals like Mr. Rodas who are responsible for distributing lethal drugs, like the fake pills containing methamphetamine in this case, to the citizens of Rhode Island," said DEA New England Division Special Agent in Charge Brian Boyle.

"Illegal drug distribution ravages the very foundations of our families and communities so every time we take methamphetamine off the streets, lives are saved," he added.