Doctors are scrambling to get to the root of Joe Jackson’s medical problems following his hospitalization Wednesday. The father of 11 visited a doctor for a routine checkup on Wednesday, which led to his admission into the hospital.

According to a report from Us Weekly, Jackson visited the doctor because he wasn’t feeling like himself over the weekend. Doctors weren’t immediately sure what may be troubling him, but a source noted that his temperature was significantly higher than normal. Medical professionals reportedly feared the Jackson family patriarch may have suffered a stroke because of his medical history. Hospital staffers were unsure initially “which way it would go,” though Us now reports Jackson’s condition is stable. He has had several visits from family members since being admitted to the facility.

“He wasn’t feeling well over the weekend and last week, and he was very sick, so they made an appointment for him to see his doctor and the doctor admitted him to the hospital,” a source told Us. “They couldn’t really pinpoint what was wrong with him. He had an extremely high fever.”

Jackson, 87, has a troubling medical history. In August 2015 he visited São Paulo, Brazil, for his birthday. While there, Daily Mail reported that he had a stroke and several heart attacks. He is believed to have spent the night leading up to his medical disaster partying. During his night on the town, he reportedly took numerous Viagra pills, which are believed to have contributed to his condition.

Many feared the stroke would leave Jackson with lasting complications. After the news broke, TMZ reported that Jackson, who was hospitalized at Albert Einstein Hospital in Brazil, may be left blind — at least temporarily. He is said to have awoken in the hospital to dizzy spells and was having problems with his vision. It was unclear at the time whether the complications were a result of the stroke or his diabetes.

None of Jackson’s children, including Janet Jackson, have spoken out about his condition.