This news follows an earlier report that Lanza may have been motivated by a desire to outdo Anders Behring Breivik, the Norwegian man who killed 77 people in July 2011, law enforcement sources told CBS Evening News.
The unnamed CBS sources said Lanza saw himself as being in direct competition with Breivik, who killed eight with a bombing in downtown Oslo before he moved to a nearby island where he hunted down and fatally shot 69 people.
According to the sources, the 20-year-old Lanza wanted to top Breivik's death toll and went to the Connecticut school on December 14 because it was the "easiest target" and had the "largest cluster of people."
Video games to blame?
The same officials also linked Lanza's actions to violent video games.
The officials, who have been briefed on the Newtown, Connecticut, investigation, told CBS that evidence shows Lanza was likely acting out the fantasies of a video game in killing 20 children and six adults at the school.
Lanza's mother, Nancy, also was found shot dead at her Newtown home. Police believe Lanza killed his mother before beginning his school rampage.
He took his own life with a handgun as authorities closed in.
Police dismiss report
A spokesman for the Connecticut State Police dismissed the CBS report, calling it speculation.
"It's inaccurate ... I talked with CBS and told them that," Lt. Paul Vance told CNN. "We are dealing with a deceased shooter and trying to rebuild history."
Vance, however, did not dismiss the notion that investigators may have looked at the Norway shooting.
"We'll look at everything," Vance said. "One thing leads to another."
Authorities have been largely tight-lipped about their investigation.
Hundreds of state troopers, detectives and other law enforcement personnel are analyzing every round of ammunition fired, examining the gunman's medical history and computer use and talking to witnesses, Vance said previously.
A final report on the Newtown shooting is expected this summer.
Vance released a statement Tuesday afternoon that didn't refer to any specific news reports but denied that any information came from the state police.
"The unfortunate origin of unsubstantiated details of this case are both hurtful and, many times, inaccurate," Vance said in the statement.
According to the news release, no information will be released until the investigation is finished, but detectives have no date when they will wrap up their interviews and evidence gathering.
The Norway attacks
July 22, 2011, will live long in the memory of all Norwegians after the carnage that unfolded that day.
After detonating a bomb outside the prime minister's office in Oslo, killing eight people, Breivik took a ferry to Utoya Island and embarked on a shooting spree that took the lives of another 69 people attending a youth camp.
Authorities said Breivik roamed the lake island shooting at campers, before members of an elite Norwegian police unit took him into custody.
In August 2012 Breivik, who boasted of being an ultranationalist who killed his victims to fight multiculturalism in Norway, was judged to be sane at the time of the attack.
He was convicted of voluntary homicide and committing acts of terror and sentenced to 21 years in prison.
CNN's Susan Candiotti contributed to this report.