A go-karting track has been ordered not to reopen until an investigation into suspected carbon monoxide poisoning has concluded.
Fifty-six people attended hospital with symptoms including headaches and nausea after visiting Gridline Racing in Lincoln on Tuesday evening. One remained in hospital on Thursday.
The Dunford Road centre closed after Lincolnshire Police and health officials said they would carry out an investigation.
Speaking on Thursday evening, Simon Walters, strategic director of communities and environment at Lincoln Council, said: "Our investigation into Tuesday's incident has now commenced. As part of this, earlier this afternoon we served a prohibition notice on the business. This prevents them from operating while the investigation takes place."
Gridline apologised following the incident, saying in a statement: "We are extremely sorry to all those affected.
"All of us at Gridline are incredibly upset by the news and would like to assure you all that we will update again once we understand the situation and the investigation is complete."
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