SPRINGFIELD — Police arrested four people Friday on gun and drug charges after a search of a home with three young children turned up a large-capacity weapon, heroin, cocaine and a baby bottle filled with what is believed to be a dangerous prescription drug.

The arrests were part of a months-long investigation being conducted by the Police Department’s Firearms Investigation Unit under the direction of Lt. Jamie Bruno, along with other state and federal law enforcement, said Ryan Walsh, police spokesman.

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