Due to Jordan rotten meat a child died and 800 people were poisoned close to Amman, the restaurant had been offering cut-price shawarmas, the rotisserie meat snack, local media said.
Health officials discovered that the meat had not been stored in the refrigerator in what were heatwave temperatures.
Three people, including the restaurant owner, have been arrested.
The five-year-old boy was part of the 826 people rushed to hospital after the first cases of food poisoning were traced in the Ain al-Bashra area of north-west Amman on Monday evening, health officials said.
The boy suffered heart failure and doctors failed to save him, Mohammad Abed, the director of Prince Hussein Hospital, told Petra news agency.
As of Wednesday four people were in a critical condition and 321 remained in hospital in a stable condition, Health Minister Saad Jaber said.
“All those affected said they had eaten meals from the same restaurant,” he was quoted by the AFP news agency as he was saying.
Local media said that the shawarma meal had been on special offer at half its normal price, resulting in a higher than normal number of diners.
Health ministry official Adnan Ishaq told state television that the meat had become infected because it was not stored in the refrigerator, and laboratory tests had detected bacteria in the meat and poultry.
Jordan has been experiencing high temperatures in recent days, with Amman exceeding 40C (100F).
Mr Jabar said an investigation into the poisoning outbreak was still under way and “any offender will be held accountable, regardless of who they are”.