KALAMAZOO, Mich. (AP) — Southwestern Michigan authorities say they cannot conclusively identify the person or people responsible for online threats to Kalamazoo College faculty members.

Kalamazoo County Prosecutor Jeff Getting said Friday his decision not to file charges is based on new information supplied by the college and Kalamazoo Department of Public Safety. A police investigation had been focused on two students in connection with the threats from March as well as anonymous postings school officials described as “racist, anti-Semitic, sexist and homophobic.”

Authorities say both students have denied any involvement.

Police and school officials have offered differing accounts of the timeline of events. Police Chief Jeff Hadley tells The Kalamazoo Gazette that investigators “tried to be as thorough as possible in light of it being a very complex and unusual case.”