SANTA CRUZ, Calif. -- Another investigation of the Santa Cruz Police Department will soon be under way after an independent auditor said the department's investigation into itself will not suffice.

The department released a 600-page report to the public on Friday, which concluded that public safety was at stake on New Year's Eve and that police had no alternative but to spy on a group planning a New Year's Eve parade.

But an independent auditor said the department looking into itself is a conflict of interest.

Police auditor Bob Anderson said the problem is that Deputy Chief Kevin Vogel gave the order to conduct the undercover operation to begin with and then was in charge of the investigation after the fact.

"The problem I had with it is that one of the most important decisions being reviewed is the decision that was made by the person who did the investigation," Anderson said.

The group that was the target of the undercover operation is Last Night.

On Monday, Last Night members and supporters staged a rally at City Hall, where the Public Safety Commission was scheduled to meet. The group demanded an independent investigation and now they've got it.

The Santa Cruz city manager gave approval for a supplemental investigation, which Anderson will begin later this week. He said he anticipates the investigation will last about a month.