Roberto Santiago - on suspension from his job as executive director of the nonprofit Concilio because of an employee's sex allegation - was reinstated last week after an investigation by an outside law firm, the president of the agency's board said.

Santiago, 51, was "very happy to be back" at work on Thursday, said a friend, who spoke on condition of anonymity.

"He has a lot of work to catch up on," the source added.

Santiago, a Latino community leader who has headed the agency since 1996, had been placed on administrative leave with pay on March 31 after a female Concilio employee made allegatins of sexual impropriety against him and notified police.

The Special Victims Unit launched an investigation into the matter on March 23, but the case was closed June 1 after the District Attorney's Office declined to file charges against Santiago, detectives said.

The alleged victim, who continues to be employed by Concilio, claimed that Santiago had touched her breasts, according to two sources.

Santiago made $95,065 in salary and an additional $16,807 in benefits, according to the 2007 tax filings for Concilio, which is based in North Philadelphia and is the oldest Latino-oriented social-service agency in the state.

Santiago took a leave from his post on the city's Civil Service Commission.

Board members can make up to to $17,500 a year for serving on the commission, according to the Mayor's Office.

As of last week, Santiago had not been reinstated on the commission, the Mayor's Office said.

Santiago did not return calls seeking comment placed to his office and home.

When asked about a police investigation, Concilio Board president Tony Valdes said:

"Nothing has been brought to our attention. We're not aware of any investigation."

Valdes declined to say what the investigator's report contained, citing "HR and personnel" issues. But according to multiple sources in the Latino community, the female employee, whose name is being withheld by the Daily News, and Santiago were in the midst of a mutual long-term relationship.

The investigation, spearheaded by Michael J. Torchia, with Semanoff Ormsby Greenberg & Torchia, LLC, in Huntingdon Valley, was completed by April 27.

It is unclear why it took the board five- and-a-half-weeks to announce the reinstatement. *