FORT MORGAN, Colo. (CBS4) — Undercover cops made a huge drug bust in Fort Morgan.

Authorities seized nearly six pounds of heroin after meeting four people in a Walmart parking lot.

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(credit: Morgan County Sheriff’s Office)

Two men are under arrest. Two others were let go.

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(credit: Morgan County Sheriff’s Office)

The heroin is worth an estimated half million dollars.

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(credit: Morgan County Sheriff’s Office)

Police say it could be the largest heroin bust in Colorado in the past decade.