PHILADELPHIA -- A Pennsylvania district attorney says Bill Cosby will not face charges stemming from a woman's allegation that he fondled her.

"The District Attorney finds insufficient credible and admissible evidence exists upon which any charge against Mr. Cosby could be sustained beyond a reasonable doubt," Montgomery County District Attorney Bruce Castor said in a statement.

Castor added, "The District Attorney reviewed statements from other persons claiming that Mr. Cosby behaved inappropriately with them on prior occasions. However, the detectives could find no instance in Mr. Cosby's past where anyone complained to law enforcement of conduct, which would constitute a criminal offense."

"The District Attorney concludes that a conviction under the circumstances of this case would be unattainable. As such, District Attorney Castor declines to authorize the filing of criminal charges in connection with this matter," the statement said.

On Jan. 28, Castor confirmed police and his office were investigating an incident that reportedly occurred in early 2004 at a home owned by Cosby in Cheltenham Township.

Police in Canada filed a complaint in January on behalf of a woman who once worked at Temple University in Philadelphia, and claimed she was drugged and fondled at that home in suburban Philadelphia more than a year ago.

That alleged victim is now living near Toronto.

Castor said Cosby and the woman both cooperated fully in the investigation. He said he won't make any judgment on the credibility of the people involved because he doesn't want to influence the jury in any civil case that might come out of this.

He noted that a civil case has a much lower burden of proof.

In February, a second woman, Tamara Green, came forward with similar allegations.

Green, now a lawyer in California, claimed she was the victim of an alleged sexual assault by the respected entertainer in the 1970s.

Cosby's attorneys continue to deny any and all allegations since they were first reported, and no charges have been filed against anyone.

In response to the first claim, Walter Phillips, an attorney for Cosby, has said the first allegations were "...utterly preposterous ... plainly bizarre ... and we will vigorously defend this."

And in February, after the second allegations came out, an attorney for Cosby said, "The allegations are absolutely false and that Mr. Cosby does not know the name Tamara Green or Tamara Lucier, Ms. Green's maiden name. In any event the incident described did not happen in any way, shape or form."