A 21-year-old college student who went missing in Missouri was found dead in Illinois after a weeklong search.

Melissa Oelke was found dead on Saturday, after she was last seen leaving her home in St. Peters, Missouri on March 26.

The St. Peters Police Department received reports around 12.30pm of an abandoned vehicle on Keck Road in St. Jacob, Illinois the same day she went missing. 

The day of her disappearance, Oelke left her home around 7.30am and left her cell phone behind, according to the Belleville News-Democrat.

Her father, Gerald Oelke, said she had been stressed after completing midterms at the College of Creative Studies, a private art and design school in Detroit.

He added that she had extended her spring break to focus on her mental health.

He also said that on the day she went missing, she stopped at several stores, including Target, Schnucks, and Walgreens.

Police said Oelke was last seen wearing an olive-green hooded sweatshirt, denim jeans, and black athletic shoes.

In the alert, officials stressed that finding her was critical due to her 'several medical conditions that require attention,' raising concern for her well-being.

Authorities launched a large-scale search effort using K-9 units, drones, and air support.

The investigation is ongoing, and police have said there is no threat to the public.

'We ask that you keep her family in your thoughts during this difficult time,' officials said in an update.

'Thank you to everyone who shared this post and offered your prayers.'