San Francisco — A special unit of the San Francisco Police Department is investigating how 19 people including a 6-year-old child could have eaten gummy candies at a birthday party that most likely were marijuana edibles, authorities said.The 19 were hospitalised on Saturday, but all of them were released by Monday.The unit is interviewing people to see if the candies were intentionally placed at the party to target children, which would be a serious crime, Officer Grace Gatpandan said at a news conference.But she said there could have been various ways the candies ended up at the San Francisco quinceanera, a traditional 15th birthday party."We don't want to automatically rush the assumption that this was an intentional act," Gatpandan said.Final laboratory results weren't available on Monday, but officials say some of the hospitalised patients tested positive for THC, the main psychoactive ingredient in marijuana. Preliminary findings show the candies contain THC, public health officials said.Thirteen of the patients were 18 or younger. The youngest was 6.Police did not name the Oakland company that catered the party and provided the food, or say how the gummies were presented.The prices of the candies vary widely, but they typically can be bought for about $25 for a pack of 10.Dr Craig Smollin, co-director of the San Francisco branch of the California Poison Control Center, said ingesting edibles is not fatal.The people hospitalised showed symptoms consistent with the effects of edible cannabis, including rapid heart rate, high blood pressure, lethargy and confusion.Authorities are concerned about making sure marijuana edibles that are attractive to children — such as gummy rings — do not get into their hands.The event could serve as a warning about the dangers of edibles, which can be extremely potent, said Dr. Tomas Aragon, the health officer of San Francisco."A situation like this, where they were consumed by unsuspecting people, and many children, is greatly concerning," he said.