PORTLAND -- The handgun that a teacher's aide brought into the Riverton Community School on Wednesday wasn't loaded, said detectives who are investigating the incident.

The aide has a permit to carry a concealed firearm but didn't realize that the gun was in her swim bag when she entered the elementary school, Capt. Ted Ross said Thursday.

"It appears to have been an unfortunate oversight," Ross said. "There's nothing to suggest that she intended to bring the gun into the school."

Ross said police continue to investigate the incident. When they're finished, the Cumberland County District Attorney's Office will decide whether to charge the woman with a crime, he said.

Under Maine law, possession of a firearm on school property is a misdemeanor that carries a maximum six-month jail sentence. Police and school officials haven't identified the aide, who has been an educational technician at the 500-student school for many years.

According to preliminary police reports, the aide set down the swim bag when she entered the cafeteria at the start of the school day. The bag was unzipped and subsequently tipped over, revealing the gun inside, Ross said.

Several students saw the gun and one of them pointed it out to a school employee who was standing nearby, Ross said. That employee told the students that the gun was a toy and called it to the attention of the bag's owner, Ross said. The aide immediately removed her bag containing the gun from the school, put it in her car and reported the incident to Principal Nancy Kopack.

Kopack notified police and put the aide on paid leave pending an investigation by school officials. She also sent an automated telephone message Wednesday afternoon informing parents of Riverton students about the incident.

On Thursday, Kopack sent a letter to parents that contained the information she provided in the automated call.

"I want to share an unfortunate incident that happened today," Kopack wrote. "A staff member inadvertently brought a handgun into school. It was immediately removed from the building when she realized what had happened. At no time were students in any danger or threat of danger.

"This is a highly regrettable incident that should not have happened," she continued. "The staff member involved is very upset and sorry for any worry it causes our school community."

Superintendent Jim Morse said he will decide how to discipline the employee after school officials and police complete their investigations. It could range from a verbal warning to dismissal.

Morse said he hopes to resolve the matter by the end of November. Afterward, Kopack will likely hold an informational meeting for parents and he will issue a formal letter reminding school employees that state law and school policy prohibit firearms on school property.

Morse and Kopack got several calls from parents on Thursday, Morse said. Some were upset about the incident. Others appreciated the school district's quick response with its new automated notification system.