The threat has passed at a Southern Cross University campus on the NSW north coast that was placed in a three-hour lockdown after an allegedly threatening phone call.

About 1.30pm, a man phoned Casino Police station and made "a number of threats ... in relation to the use of firearms" at the Lismore campus, Acting Region Commander for the Northern Region Wayne Humphrey said.

"It was a single phone call that went for some time, long enough for a police negotiator ... to converse with the male for some period," he said.

"Inquiries will determine if this was an elaborate hoax or if there were some substance to what occurred. "