Federal authorities in San Diego say they have seized one of the largest loads ever in the U.S. of the potent synthetic opiate Fentanyl.

An indictment unsealed Monday says federal drug agents seized over 97 pounds of the drug, most of it from a house in San Diego.

A U.S. attorney's statement says the drug is so powerful that the amount represents millions of lethal doses. Drug traffickers use it to strengthen heroin or make counterfeit painkiller pills.

Three people, Jonathan Ibarra, Hector Fernando Garcia and Anna Baker, were indicted for possession of the drug with intent to distribute.

Court papers say the defendants discussed having Baker smuggle the drugs on three separate trips. In November, agents stopped Baker's rented vehicle and found some of the fentanyl, then discovered the rest in a search of her house.