VALPARAISO, Ind. (AP) — Valparaiso University in Indiana has increased security and warned students via Twitter and email after receiving a vague threat through some graffiti.

The school says the threat claimed ‘‘dangerous and criminal activity’’ would occur on campus during the university’s daily chapel break on Friday. The message provided no details.

The school says the FBI and police searched the campus but found nothing suspicious.

Senior Chris Likeness says the school issued two alerts.

University spokeswoman Nicole Niemi says classes and other regular activities are continuing as planned.

The university tweeted that Valparaiso did not receive a bomb threat as schools in Texas and North Dakota did. Valparaiso called its situation ‘‘substantially different.’’