SARATOGA — West Valley College was evacuated after an anonymous letter containing a “credible bomb threat” was found on campus Tuesday morning, according to a college spokesman.

Authorities issued an “all-clear” following a sweep of the campus with a bomb-sniffing dog.

The evacuation began shortly after students working at the Campus Center information desk found the letter around 9:15 a.m., said Scott Ludwig, a spokesman for West Valley College. The letter was turned over to the director of the center, who notified campus police.

Administrators were advised of the letter about 10 minutes later and made the decision to evacuate after some discussion, Ludwig said.

“The details were such that it was deemed to be a credible threat,” he said when asked about the content of the letter.

The college used automated alert and campus audio systems to notify students and faculty about the bomb threat and evacuation, Ludwig said. The news was also shared on social media.

About 5,000 people were evacuated starting around 9:45 a.m., Ludwig said. Classes were canceled for the rest of the day.

Campus police, who were assisted by the Santa Clara County Sheriff’s Office and the Campbell Police Department, did not find anything suspicious during the search, Ludwig said.

Ludwig declined to comment when asked whether authorities had identified a suspect or a person of interest.

Classes were expected to resume Wednesday.

Contact Mark Gomez at 408-920-5869. Follow him at Twitter.com/MarkMgomez.