Health officials said evidence of E. coli bacteria was found at a hydration station at the Erin Hills golf course, site of the U.S. Open in Erin, Wisconsin.
The Washington Ozaukee Health Department said in a release that no incidents of illness had been reported.
The department identified the bacteria in a sample collected at the 12th hole.
The water line to the contaminated hydration station was shut off Thursday morning, but some visitors may have consumed water from the station between Tuesday afternoon and Thursday morning.
The USGA said it would provide complimentary bottled water at all hydration stations for the duration of the tournament.
"The safety and security of our guests is of paramount importance to the USGA," association spokesman Jeff Altstadter said in the statement.
According to the Centers for Disease Control and Prevention, certain types of E. coli may be harmless but others that cause diarrhea can be transmitted through contaminated water or food, or through contact with animals or persons. The incubation period is usually 3-4 days after the exposure, but may be as short as one day or as long as 10 days.