(Reuters) - A Maryland woman who ordered a meal at a Sonic Corp fast-food restaurant got something extra with her French fries - a bag of marijuana.

Carla McFarland, 35, of Frederick, Maryland, and her children, ages 6 and 8, were about to eat a chicken strips lunch on Thursday when she discovered a small, green plastic bag of marijuana in her fries, according to the Frederick County Sheriff's Office.

Spokeswoman Lieutenant Jennifer Bailey said on Friday no arrests had been made and the incident is under investigation.

McFarland posted about her find on Facebook, along with a photo of the bag.

"I order, food comes, I open a bag and this is what I see after 3 double takes ... yes that's what it is," she wrote.

McFarland said a Sonic employee claimed ownership of the marijuana and was promptly fired. McFarland also called police.

Sonic spokesman Patrick Lenow said restaurant management contacted police and was cooperating with authorities.

"The employee involved is no longer associated with the company, and the franchisee is conducting an investigation to ensure the issue is fully resolved,” he said in a statement.

The Frederick franchise location opened last month.

Possession of small amounts of marijuana is a misdemeanor in Maryland.

(Reporting by John Clarke; Editing by Ian Simpson and Dan Grebler)