PORTAGE, Mich. (AP) - Authorities say two students have been arrested following an investigation into a threat involving a school in southwestern Michigan. MLive.com reports a potential threat was investigated this week involving Community High School, the Portage Public Schools' alternative high school program. Meanwhile, a threat by an 18-year-old student of a shooting at Otsego High School led officials to keep students home Thursday. And WDIV-TV reports a 15-year-old student was arrested Wednesday following a threat involving Melvindale High School in suburban Detroit. There have been a number of threats in Michigan since a massacre that killed 17 high school students and faculty last week in Florida. In the Flint area, a letter to parents says a student who made a threat involving Clio schools was arrested and held pending possible charges.