SALISBURY — An Erwin Middle School teacher is accused of exchanging inappropriate Facebook messages with a female student.

The Rowan County Sheriff’s Office on Thursday charged the teacher with taking indecent liberties with a student.

Mark Robert Dexter, 42, of the 100 block of Brookestone Way, remains in the Rowan County Detention Center under a $150,000 secured bond. He has resigned from his teaching job.

Authorities said that on Monday, the Sheriff’s Office received a complaint from the family of the girl. Investigators determined that Dexter had been communicating with the girl, who is not his student, via Facebook messenger. Based on the content, authorities say, it appears the two were in an online relationship.

The date and time stamps of the messages show that Dexter was sending the girl messages while he was at the school from his personal cellphone. The messages indicate Dexter was making plans for the student to come to his home, but investigators say no evidence suggests she had been there yet.

Over the course of eight days, thousands of messages were exchanged between the two resulting in more than 400 pages of evidence. The messages date back to Sept. 9.

Dexter was confronted with the report by a sheriff’s detective, and authorities say he admitted exchanging the messages with the girl. Digital evidence was taken from electronic devices of both the victim and Dexter, along with the data from Facebook.

Dexter taught math and social studies at Erwin Middle, where he had been employed since August 2005. He began his teaching career in Rowan-Salisbury Schools at Morgan Elementary in 2004.

Dexter resigned from his position at Erwin on Wednesday.

Investigators worked closely with the Rowan County District Attorney’s Office, and a warrant was obtained Wednesday charging Dexter in this case.

Rita Foil, spokeswoman for Rowan-Salisbury Schools, said Erwin Middle Principal Daniel Herring met with his staff and is communicating with parents in the Erwin community through various avenues. The school system is supporting the Erwin students and staff with additional counselors for as long as needed, she said.

“While we cannot address specific incidents, we are sad and heartbroken anytime we receive reports of inappropriate conduct towards any of our students,” Foil said in an email. “We have policies and procedures in place to handle these situations immediately. We are also fortunate to have excellent relationships with law enforcement as we partner together to conduct investigations and to keep our students and schools safe. We will continue moving forward in keeping safety a top priority in our schools.”

Investigators arrested Dexter late Wednesday night at his Granite Quarry home and he was placed in the Rowan County jail.

Officials said investigators are continuing to review evidence and speak with potential witnesses. Additional charges may be pending.

Post reporter Rebecca Rider contributed to this story.