LAWRENCE, Mass. (AP) — Authorities in Massachusetts have arrested eight people they say were involved in a major fentanyl trafficking operation based in the Merrimack Valley.

Authorities also seized large quantities of fentanyl during the course of the investigation, according to a statement Monday from the office of Attorney General Maura Healey.

The arrests were the result of a months-long investigation involving multiple federal, state and local law enforcement agencies.

Authorities last week executed search warrants at six locations in Lawrence, yielding approximately $150,000 in cash and 700 grams (1.5 pounds) of fentanyl and crack cocaine. During the course of the investigation, authorities seized an additional 1,800 grams (4 pounds) of fentanyl and 500 pressed fentanyl pills.

Six Lawrence residents and two from Lowell were arrested on drug charges and held on bail ranging from $7,500 to $200,000.

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