Milwaukee ? Police now believe people who know something about two missing Milwaukee boys are withholding information that could lead to a major break in the investigation.

“We have reason to believe there are individuals with information that is pertinent to this investigation who for reasons unknown to us right now aren’t coming forward,” Milwaukee Police spokeswoman Anne E. Schwartz said at a Friday afternoon briefing.

The news was the first major development announced in the five-day search for Quadrevion Henning, 12, and Purvis Virginia Parker, 11, last seen the afternoon of March 19.

Schwartz said information developed in the department’s joint investigation with the FBI led them to the conclusion that someone is withholding information that could prove useful to authorities.

Despite receiving hundreds of phone calls and tips in the days after their disappearance, police had maintained they had no leads, until Friday afternoon.

“We are making a specific plea to those people to please come forward, we need them to come forward as soon as possible,” Schwartz said.

Schwartz would not give more information about the developments, or characterize who authorities were appealing to.