The University of Colorado, Denver said the U.S. Postal Service delivered the package to its medical campus Monday, and it was immediately investigated and turned over to authorities within hours.
Fox News' website reported that former neuroscience graduate student James Holmes sent a notebook to the university containing scribblings of stick figures being shot and a written description of an upcoming attack. The package containing it was addressed to a psychiatrist at the school, the website reported. It was unclear if Holmes, 24, had had any previous contact with the person. The neuroscience program that he withdrew from on June 10 included professors of psychiatry.
He is accused of opening fire on a theater showing the new Batman movie, killing 12 people and injuring 58.
NBC News, citing unnamed sources, reported that Holmes told investigators to look for the package and that it described killing people.
The FBI and other law enforcement agencies refused to confirm the reports to The Associated Press.
U.S. Postal Service spokesman David Rupert said the agency's inspectors have no direct knowledge of the package reportedly containing the notebook. He said no one has contacted the Postal Service for assistance in the investigation.
Citing unnamed law enforcement sources, Fox News' website reported that Holmes sent the notebook in a package that had sat unopened since July 12.
The university said the report that the package sat uninvestigated that long is inaccurate. A spokeswoman declined to comment further, citing a gag order issued by a judge in the case.
Before the gag order was issued, police said Holmes received more than 50 packages at the school and his home that apparently contained ammunition, combat gear and explosive materials that he used in the attack and to booby-trap his Aurora apartment.
The building was evacuated for days while authorities rendered the apartment safe and collected evidence. Residents were allowed to return Wednesday evening.
Holmes' defense team also briefly visited the apartment building Wednesday and left without answering reporters' questions.
Holmes was allegedly stockpiling for the attack while he studied at the school's neuroscience program. He bought a shotgun and pistol in May, authorities say. On June 7, the date he took a year-end oral exam, he bought an assault rifle. He filed paperwork to leave the program three days later and did not provide a reason, the university has said.
On June 25, he filed an application to join a private gun range in eastern Colorado, but the club's owner, hearing what he described as a "bizarre" outgoing voice mail on Holmes' cellphone recorded in a low voice with heavy-breathing, told his staff to watch out for the man. Holmes never came to the range.
Holmes grew up in California.