Jackson is still experiencing an irregular heartbeat and is in the hospital's intensive care unit in São Paulo, the Albert Einstein Israelite Hospital told the Associated Press.
The patriarch of the musical Jackson 5 posted a statement from his hospital room on Monday thanking his fans for their support.
"To my family, friends, acquaintances and fans all over the world. I want to thank you all for your prayers, unwavering support and kind well wishes during these trying times. Through God's intervention the wonderful Doctors, Nurses and caretakers at the Albert Einstein Sao Paulo hospital have taken great care of me," he wrote. "God willing, I should be able to make a quick recovery and travel back home soon. Thank you all once again for your prayers and support."
Earlier, local media reported that Jackson missed his own party because of his trip to the hospital, according to USA Today. Despite the unfortunate turn of events, Jackson had been (and remains) in high spirits. His website documented a countdown to his birthday by posting photos of his outings. In one snapshot he's surrounded by jovial staff at a local restaurant. In another, he shows off a toothy grin as he receives a personalized soccer jersey from the Corinthians, a soccer team.
An email from PEOPLE to the Albert Einstein hospital was not immediately returned. An email sent to Joe Jackson's website resulted in a copy of Jackson's online statement but no further comment about his condition.
Jackson is slated to leave Brazil on Tuesday, though it is not known whether he will be healthy enough to do so, according to the AP.
He has suffered minor strokes in the past, including one in 2012.