Freshman Michael Evan Anderson of Mission Viejo, Calif., died Friday morning on the roof of the three-story dorm.
The Arizona Daily Star (http://goo.gl/XnohS6 ) said the investigation includes analyzing security video at a fraternity house to determine where there was a party there and interviewing students and a cab driver.
Court documents indicate that detectives also searched Anderson's room in the dorm and found suspected marijuana and glass smoking pipes.
Police Sgt. Filbert Barrera said toxicology test results which could confirm whether Anderson was impaired by drugs or alcohol won't be available for several weeks.