BOSTON (AP) — Gov. Charlie Baker says the recent surge in confirmed coronavirus cases in Massachusetts is being driven in large part by an increase among younger people.

The Republican said Tuesday that 15% of new cases in April were among people under the age of 30 but that 37% of the new confirmed cases are people in that age group.

He urged people to stop holding indoor parties and reminded people that outdoor trick-or-treating on Halloween is much safer than an indoor party.

Baker blamed the closures of indoor ice skating rinks last week after a surge in cases linked to hockey games on parents and coaches who didn’t cooperate with state contact tracers.