Pele has re-entered an intensive care unit at a hospital in Sao Paulo, ESPN Brasil reported on Friday.
The 80-year Brazilian football legend had left the Albert Einstein hospital on Tuesday following successful surgery to remove a tumour in his colon earlier in September.
The hospital said it had no new information.
After leaving the ICU earlier this week, Pele said in a message to fans on Instagram that he was ready for “90 minutes, plus extra time.”
Pele has suffered from hip problems for years and cannot walk unaided.
In recent years, he has also undergone kidney and prostate procedures.
His public appearances were already being cut before the Covid pandemic and since then he has made few unnecessary forays outside his house near Santos.
After leaving the ICU earlier this week, his daughter Kely Nascimento posted on social media to confirm the procedure had been successful and that Pele was not in any pain following the surgery.
“He is strong and stubborn and with the support and care of the brilliant team at Einstein and all of the love, energy and light that the world is sending, he will get through this,” she said.
Pele won the 1958, 1962 and 1970 World Cups and remains Brazil’s all-time leading scorer with 77 goals in 92 matches.