Norovirus was the cause of some cases of nausea, diarrhea and chills that afflicted players and staff at the BNP Paribas Open tennis tournament in March.

The Riverside County Department of Disease said Monday the illness knocked several top players out of the world-class BNP event at the Indian Wells Tennis Garden.

“Some individuals were tested and we did have some positive results for norovirus,” said Barbara Cole, director of disease control for the Riverside County Department of Health.

“We did have some people that were linked to the tournament, but we can’t say definitively that everyone who was ill had norovirus.”

Among the players who withdrew from the event were Nikolay Davydenko, Vani King, Gaels Monfils, Francesa Schiovone and doubles specialist Mike Bryan. Both women’s No. 1 seed Victoria Azarenka and men’s champion Roger Federer complained about symptoms during the two-week event, though Federer insisted he had the illness before arriving in Indian Wells.