The NRP stopped about 600 vehicles during R.I.D.E. programs in St. Catharines and Port Colborne.
Officers administered 26 roadside screening tests on Monday and four drivers found themselves in the warning range.
They each face a three-day licence suspension.
The officers also issued tickets for traffic related offences.
2 Niagara men arrested by Toronto Police
Accessed rooftop to take pics for social media
Niagara Parks Tree Planting Day - Sat. Oct. 24
The free event takes place from 10AM-Noon
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