HARTFORD, Conn. (AP) – Federal authorities in Connecticut say they have seized about 20 kilograms (44 pounds) of heroin and fentanyl and arrested 13 people.

The arrests and drug seizures on Thursday during raids at a dozen locations in Connecticut and western Massachusetts were the conclusion of a monthslong investigation.Related: Police on scene of drug operation in Hartford

U.S. Attorney Deirdre Daly in a statement said the drugs were packaged for sale in hundreds of thousands of small bags. Investigators also seized a quantity of horse tranquilizer often used as a heroin additive and seven guns.

Of the 13 people arrested, 10 were from Connecticut, two were from Massachusetts and one was from New Jersey. All were ordered held during their court appearances Thursday on drug possession and distribution charges.

Prosecutors say much of the drugs were sold at a small Hartford store.

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