03/09/2013 at 08:00 PM EST
is still in the hospital.
The Fashion Police
star Tweeted Thursday that doctors are trying to figure why she had a seizure
on the set of her E! show earlier that day.
So far, they're still stumped.
"She is scheduled to have more tests," a source told PEOPLE Saturday. "But she has not had another seizure since she was admitted." The source adds that Osbourne, 28, is on medication.
Although TMZ says
Osbourne could possibly have epilepsy, which causes seizures, her rep says that may not be the case.
"There is absolutely no confirmed diagnosis regarding Kelly's condition at this time," her rep said. "She is under a doctor's care and they are continuing to run tests."
While taping the show on Thursday, Osbourne reportedly turned to fill-in host Melissa Rivers and said she didn't feel well before falling out of her chair and shaking.
"Kelly is fine," her rep said Saturday, "and thanks everyone for their continued support."
Reporting by JULIE JORDAN