More than two dozen employees at the San Francisco Public Utilities Commission are at the center of an investigation and are suspected of sharing porn and gambling using city time and computers.

Sources close to the investigation said 15 water department supervisors working at SFPUC yards in Sunol, Millbrae and San Francisco are accused of sharing pornographic images and gambling, all while using city computers on overtime.

Out of the five classifications within the Plumbers Union, sources said the employees under investigation are among the top three: foremen, general foremen and gatemen.

"I can't comment on any individuals or their classifications involved; however, it's pretty standard HR practice to take job position into account when determining the appropriate level of discipline," said Tyrone Jue of the SFPUC.

SFPUC officials said they started an investigation months ago after a whistle-blower came forward.

While investigators don't believe any of the activity was criminal, sending and receiving explicit images and gambling are specifically prohibited in San Francisco's employee handbook.

Associate professor at Berkeley's Haas School of Business Ernesto Dal Bo said taxpayers should be concerned about supervisors' personal use of city resources, even if it wasn't for something as offensive as pornography.

"It's important to realize this is wrong, but we have to realize this is wrong for the right reasons," said University of California, Berkley Ernesto Dal Bo. "One important aspect of positions of leadership is that other people in the hierarchy are looking up to you and taking cues as to what constitutes acceptable behavior."

KTVU reached out Thursday to the Plumber's Union, Local 38, but has not received a response.

The employees in question are still on the job, but sources said the city could go to the union with its findings to discuss discipline as soon as Friday.