(CNN) A student working on his doctorate at a New York university was found dead by his roommate earlier this month five hours after the student made an "unintelligible" 911 call for help, according to a police official.

First responders couldn't find Yeming Shen because his 911 call February 10 was not understandable and it was made on his foreign-issued cell phone that was only traceable to an area -- not a specific address -- in the city of Troy with several apartment buildings, Capt. Steven Barker said Friday.

Officers and firefighters went around knocking on doors at the apartments near Rensselaer Polytechnic Institute, but couldn't find the man, who called 911 at 11 a.m., he said.

Around 5:45 p.m., Shen's roommate returned to their apartment, found him dead, and called 911, Barker said. A preliminary autopsy determined he died of influenza , Richard Crist, director of operations for Rensselaer County, said earlier this month.

"The incident draws to attention the severity of the flu and the devastating effects it can have," Barker said. "We continue to extend our thoughts to the family and friends of Mr. Shen, as well as the responders involved throughout the incident."