Hugo Chávez is expected to miss an important regional summit in Brazil on Friday, raising fears that the Venezuelan president’s health may have taken a turn for the worse.

Chávez was absent from Thursday’s preparatory meeting for the Mercosur summit, and a spokesman for the Venezuelan ministry of foreign affairs refused to say whether he would attend on Friday.

“I have no information on the matter. President Chávez could very well surprise us there, or we could be receiving a statement in the next minutes,” a spokesman, Victor Castellanos, told the Guardian.

Fears about Chávez’s health have resurfaced since his trip to Cuba last week for follow-up treatment after undergoing chemotherapy and surgery this year.