PROVIDENCE, R.I. (AP) — A police presence will resume at schools in in Cranston, Johnston and Warwick a week after police in Johnston said they received an anonymous letter threatening physical harm to elementary school children.

WPRI reports that different strategies will be put in place after the end of the Columbus Day weekend.

Police in Cranston and Johnston will be at the school all day this week.

In Warwick, police will appear at arrival and dismissal and also will patrol the schools at different times during the day.

Meanwhile, investigators are working to track down suspects while proving the validity of the handwritten threat.

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