NEW YORK (CNN/Money) - Though 64 college basketball teams won enough games to qualify for the NCAA tournament, March Madness is a losing proposition for most companies.

U.S. companies stand to lose $504 million in lost productivity as employees check sports Web sites, tune in to game broadcasts and put the finishing touches on office pools, according to employee management firm Websense Inc.

About 75 percent of U.S. workers participate in office wagering and 30 percent bet specifically on college athletics, according to the company, citing Vault.com and a report from the Society for Human Resource Management.

In addition to losing employee productivity, companies risk bad publicity or legal troubles from office pools gone awry. A middle manager for AT&T was recently arrested after he organized a football pool and pocketed 10 percent of the $30,000 he collected.

"Seemingly harmless office pools can introduce the lure and excitement of gambling to the 5 to 8 percent of the population who cannot handle social gambling," Dr. David Greenfield, CEO for the Center of Internet Studies, told the company. "A company-sanctioned office pool may be the first experience a person has with gambling, and employers need to be cautious about potentially problematic activities."

Only 34 percent of companies have written policies or unwritten "understandings" on sports wagering while at work, the company said.

Americans wager about $3 billion on NCAA basketball tournament games, according to Websense, citing the Federal Bureau of Investigation.