Attorney General Ken Salazar (search) has asked for a grand jury to look into "two remaining questions" about the Jefferson County sheriff's investigation of the Columbine High School shootings, District Attorney Dave Thomas said Thursday.

Thomas did not say what the questions were. He said they stem from Salazar's investigation into why sheriff's investigators never followed up on a 1997 report about ominous comments by one of the Columbine (search) killers on a Web site, two years before the killings.

The report was found in a sheriff's department binder last October.

Thomas had not decided whether to call a grand jury, spokeswoman Pam Russell said Thursday.

Jefferson County Sheriff Ted Mink asked Salazar to investigate his department's handling of the 1997 report. Salazar announced in February that he found no sign of negligence by the sheriff's department, though he found at least 15 instances of contact between law enforcement and one or both of the killers.

He also said investigators are still looking for a case file tied to the search warrant.

Eric Harris (search) and Dylan Klebold (search) shot and killed 12 classmates and a teacher at Columbine High School on April 20, 1999.

On the Web site, Harris referred to "ground zero" and boasted that he and Klebold had built pipe bombs.

Another Columbine student alerted a sheriff's deputy to the Web site, and the deputy forwarded the tip to John Hicks.

Hicks' report was found tucked inside a training manual in October.