The local fire department said they responded to a call of a possible overdose at 1.27am local time.
They say they transported a single person to a local medical centre.
There are several reports the person involved was Paris.
She is said to have been taken from the Jackson family home in Calabasas, California, on a stretcher and transported to hospital in an ambulance.
A statement on behalf of her mother, Debbie Rowe, said: "We appreciate everyone's thoughts for Paris at this time and their respect for the family's privacy."
The last message posted on Paris' official Twitter account was 12 hours ago.
It read: "Yesterday, all my troubles seemed so far away. Now it looks as though they're here to stay."
Paris is the only daughter of the late Michael, who died in 2009 aged 50.
In an interview in April, she spoke of her "incredible father" and defended her upbringing.
She said the King of Pop battled to give his children a "normal childhood"
"I have lots of memories of my father. He was an incredible father. We all loved him to death."
Paris and her siblings live with their grandmother Katherine following Jackson's sudden death.