BOSTON (AP) — A group of Massachusetts state senators plans to travel to Colorado next week to learn more about that state’s system for the legalized use of recreational marijuana.

The Senate Special Committee on Marijuana was formed last year in response to a potential 2016 ballot question that — if approved by voters — would allow pot to be used recreationally in Massachusetts by people 21 or older.

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A draft itinerary for the four-day trip starting Monday includes meetings with Colorado state officials, legislators and law enforcement.

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Committee Chairman Sen. Jason Lewis says the panel has been making progress in studying the complex issues that arise out of marijuana legalization.

Three other states — Washington, Alaska and Oregon — have legalized the recreational use of marijuana.

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