An English teacher at a small Alabama high school has been charged with having sex with at least four students and allegedly involving one in a plot to kill her husband.

Officials released few details but said the husband, a gym teacher who taught at the same school last year, was unharmed.

School officials were first tipped off to concerns about the teacher in 2004 by an unsigned letter accusing Sharon Linton Rutherford of sleeping with students, Clarke County Schools Superintendent Gerald Stephens said.

Stephens said the school investigated and informed police, but they had little to go on.

Then, on April 5, one of the students told Coffeeville High School Principal Janice Richardson that he had had sex with the 30-year-old teacher, according to Stephens and detectives.

Authorities declined to comment on the evidence but arrested Rutherford on Tuesday and charged her with solicitation of murder, rape, sexual abuse and two counts of enticing a child for immoral purposes. She was ordered held on $55,000 bond.

Clarke County Sheriff's detective Ron Baggette said two of the victims were under 16 and he was investigating to determine if more students might have been involved. He said some of the alleged encounters were on school grounds.

"I wouldn't have charged her if I didn't have enough evidence to show it is true," Baggette told the Mobile Register for its Friday editions.

Coffeeville High School, about 75 miles north of Mobile in southwest Alabama, has about 110 student.

Rutherford was put on administrative leave after she was charged. Her husband, James Rutherford, who teaches in another town, did not return calls seeking comment.

Coffeeville Mayor Faye Cotten described Sharon Rutherford as a shy woman and told the Register that she and others in the community were surprised by her arrest.

"We've all been talking about it, and what we can't figure out is, if she really did this, why she would risk everything, just everything?" Cotten told.