School activities resumed at Tufts University Monday after a bomb threat and car fire led to a sweeping investigation at the college’s Medford/Somerville campus.

In a notice sent around 1:45 p.m., students were advised they could walk freely around campus again, and that evening exams would be held as planned. Earlier, students had been advised to stay indoors and exams earlier in the day had been cancelled.

Extra police were patrolling the school Monday “for the peace of mind of the community,” the update read, adding “Thank you for your cooperation and patience during this very unusual and challenging day.”

Around 4:30 a.m. a Tufts University employee’s car was discovered burning near the school’s health center. Near the blaze, investigators found taped to the health center’s door a threatening note which referenced an ongoing labor dispute between the university and custodial staff, according to The Boston Globe.

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Crews hauled away the burned-out car from its spot at 124 Professors Row on Monday afternoon. Photos taken early that morning show flames bursting out of the vehicle’s interior.

Groups involved in the contentious labor situation — the custodial workers’ union, the on-campus group Tufts Labor Coalition — have claimed no involvement in the car fire and have condemned the incident.

Speaking with reporters Monday morning, Mary Jeka, senior vice president for university relations, said “it is not at all clear" that the dispute was the motivation for the fire and threatening note.

Authorities had evacuated and searched Cabot Hall, Braker Hall, Cohen Hall, the Health Services building, the Tisch Library and the Tisch Sports Complex after the discovery of the threat.

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The school said in an update on its website that “multiple law enforcement agencies” were investigating.

Counseling services were being made available to students and faculty, and students who felt they could not take their exams Monday night were asked to contact a doctor, a counselor or an academic dean.