The city of Somerville issued an alert shortly after 8 a.m.:
This morning Somerville Police and Fire responded to a car fire at 124 Professors Row, and discovered a suspicious note indicating bomb threats at several Tufts University buildings. The fire was extinguished and local and state police remain on scene investigating the bomb threats. At this time the buildings in question are secured until further notice. Residents are advised to remain off campus and to seek alternate routes this morning. Police will remain on scene throughout the morning to continue their investigations. Updated notification will be sent when the area has been cleared.
Boston Reddit has more info.