SULPHUR, Okla. (AP) — Oklahoma officials have closed a school for deaf students after the facility received a threatening phone call.

A spokeswoman for the Oklahoma Department of Rehabilitation Services says officials believe Thursday's threat to the Oklahoma School for the Deaf is linked to threats against a transgender student who attends another school that was shut down earlier this week over safety concerns.

Spokeswoman Jody Harlan says the call threatened "grave danger" against an employee. Students weren't in session.

School officials believe a family member of the employee made negative Facebook comments about a 12-year-old transgender girl who attends school in Achille, about 60 miles south of the School for the Deaf in Sulphur.

School for the Deaf officials called Sulphur police and the FBI.

Class was set to start Monday at the School for the Deaf, but that has been postponed.