LOS ANGELES — A mystery illness has infected some 170 people who attended an Internet conference in Los Angeles hosted by the Playboy Mansion among other venues, health authorities said on Monday.

The LA County's Department of Public Health said it is trying to contact all those who attended the three-day DOMAINfest Global Conference, for 700 Internet professionals from 30 countries.

"To date, approximately 170 individuals have reported illness with symptoms mostly consisting of fever, chills, general discomfort and some cough," it said in a statement, after the mystery illness was first reported Sunday.

"The department is investigating several locations associated with this conference, including the Playboy Mansion," it added, adding that experts had yet to determine the source or cause of the outbreak.

Officials were trying to contact conference participants who live outside the LA area, including via the California Department of Public Health, it added.

"Public Health has no information suggesting that this suspected outbreak extends beyond those individuals associated with this conference," it said.

Dozens of people became ill after they attended a February 3 fundraiser at Hugh Hefner's Gothic mansion, centre of the Playboy empire — whose Twitter feed trumpeted Monday: "Love is universal — Happy Valentine's Day!"

The Los Angeles County Department of Public Health emailed all participants Friday to warn them about a possible respiratory infection outbreak similar to pneumonia among attendees, the Los Angeles Times reported.

"It knocked me off my feet for five days," Castello Cities Internet Network Inc. co-founder David Castello told the LA Times newspaper. "I'm over it now, but I'm still feeling fatigue, which is not a good thing."

Some of those who fell ill pointed to a fog machine used at the party as the likely culprit.

The Times said many suspected their symptoms were linked to legionellosis, or Pontiac fever, a milder form of Legionnaires' disease. The ailment is usually caused by bacteria that grow in warm water and spawn in hot tubs or air conditioning systems.

The bacteria are inhaled in water vapour rather than being spread between people.