DES MOINES, Iowa?- The death of an Iowa State University student who was found in the trunk of her car outside an Iowa City apartment building last year has been ruled a homicide.

The Johnson County medical examiner issued a death certificate Thursday for 20-year-old Tong Shao, listing the immediate cause of death as asphyxia and the manner of death as homicide, the Des Moines Register reported.

Shao was a junior chemical engineering student from China. Her body was found Sept 26 in the trunk of her car. The medical examiner's office completed her autopsy report months ago, but declined at the time to publicly release it at the request of the Iowa City Police Department.

Authorities have said they're looking for Xiangnan Li, a friend of Shao's who was a registered student at the University of Iowa around the time Shao went missing in September. Authorities have said they believe he may have information about Shao's death.

A police search of Li's apartment on the day Shao's body was found seemed to show he left the apartment in a hurry. A police report says a black suitcase filled with clothing was found in the apartment, and groceries that had recently been purchased also had not been put away, including spoiled milk left on a counter.

Ames police say Li took a flight from Cedar Rapids on Sept 8 and arrived in China on Sept 10. A report by Ames police says none of Li's friends or family in China have reported seeing him.

Iowa City police said earlier this week that they have finished their investigation and have turned the case over to the Johnson County Attorney's Office.

Information from: The Des Moines Register, http://www.desmoinesregister.com