One morning in February, a CBS3 employee sat down at a computer shared by newsroom staffers. When the employee wiggled the mouse to "wake" the idle monitor, it became clear that the previous user had forgotten to log out of a Yahoo e-mail account.

The employee did a double-take: The e-mail account was registered to Alycia Lane - who had been fired as anchor six weeks before.

And yet, someone at CBS3 seemed to be reading Lane's personal e-mail.

According to sources close to the case, who recounted this version of events, the discovery ultimately triggered an FBI investigation in which Lane's former coanchor, Larry Mendte, has emerged as the prime suspect.

The CBS3 employee alerted Lane, according to several sources. Within weeks, someone - it could not be determined who - brought in the FBI.

On Thursday, after three months of quiet computer sleuthing, FBI agents seized Mendte's home computer and delivered a court order to CBS3 demanding related evidence, sources said.

Federal authorities reviewing the computer evidence have concluded that Mendte improperly accessed Lane's Yahoo account hundreds of times, sources said. Now, they are trying to determine whether Mendte used information from the e-mail to leak gossip about Lane to the media, people familiar with the investigation said.

CBS3 fired Lane in January after several embarrassing events, including one in which she was arrested in New York City for allegedly striking an officer. Those felony charges were dropped in February. In another widely reported incident last year, Lane sent bikini pictures of herself to cable sports anchor Rich Eisen. The e-mail to Eisen was sent to an account he shared with his wife.

It could not be determined yesterday how Mendte, who has been removed from the air pending the outcome of the case, became the FBI's prime suspect. His lawyer, Michael A. Schwartz of the Pepper Hamilton law firm, said that he believed Lane was the one who raised the allegations with the FBI.

Schwartz declined to elaborate about that but said, "Larry expects to continue to fully cooperate with federal authorities, and we hope to reach a prompt resolution."

Lane's lawyer, Paul Rosen of the Spector Gadon & Rosen firm, said he worried that privileged attorney-client communications he sent to Lane by e-mail may have been compromised. Asked whether he was the one who notified authorities of suspicions that his e-mail messages with Lane were being illegally accessed, Rosen said he would not comment while the investigation was ongoing.

It is a federal crime to access computer files over the Internet without authorization. If Mendte is charged and convicted of a computer-related crime, he is unlikely to face prison time, according to federal sentencing guidelines. Unless it can be proven that the crime triggered a large monetary loss, a sentence of probation is likely.

Lane has sued CBS3 for wrongful termination.

Federal officials have remained tight-lipped about the case. Patty Hartman, a spokeswoman for the U.S. Attorney's Office, said yesterday that she could neither confirm nor deny the existence of the investigation.

A CBS3 spokeswoman did not return a phone call seeking comment about the e-mail breach.

Neither Mendte nor Lane has publicly commented.

With Mendte off the air, coanchor Susan Barnett was to anchor yesterday's newscasts solo. CBS3 has appointed other staffers to make Mendte's public appearances, including tomorrow's UBS Motor Cars Under the Stars to benefit United Cerebral Palsy and Thursday's all-day station telethon to benefit Alex's Lemonade Stand, a cause that Mendte long championed. Mendte resigned from the chapter's board last week.

Current and former station employees yesterday described the Lane-Mendte relationship as cordial, even chummy, for the first year of their on-air partnership, which began in September 2003. Friction set in as both sought recognition for rising ratings, according to CBS3 newsroom sources.

Staffers said that shortly after Lane's Dec. 17 arrest, Mendte summoned workers to his office and showed them a novelty card he had found, bearing big red lips and the words "I'm a [expletive] reporter, bitch!" - which is what New York police had alleged Lane told them during their encounter.

Station sources said Mendte laughed and said he would use that as his Christmas card.

Mendte has been involved in a computer incident before, though in far less serious circumstances - on the eve of the Mid-Atlantic Emmy nominations in 2006.

While browsing the sponsor's Web site, Mendte correctly deduced that changing "2005" to "2006" on the site's address would bring up the new list of nominees. At the ceremony, before the nominations were announced, he boasted that he would win 14 nominations. He did, and then revealed how he knew.

Contact staff writer Michael Klein at 215-854-5514 or mklein@phillynews.com.