Three women in their 20s reported finding tablets in their food after they returned home from Istanbul Grill in High Street, Bognor Regis, around 2am on Sunday 29 December, police said.
Officers attended the premises later the same day and arrested two local men, aged 30 and 42, on suspicion of administering poison with intent to endanger life or inflict grievous bodily harm, police said.
They have since been released on conditional bail until 27 January while enquiries continue, confirmed police.
On Monday (30 December), police enforced a 48-hour Closure Order under Section 76 of the Anti-Social Behaviour and Crime Prevention Act 2014, on grounds that the operation of the premises has constituted a public nuisance, police said.
A spokesman said: “This is a direct result of the incident currently being investigated by police, and an application will be made to magistrates to confirm the order on Wednesday (1 January).”
Also a Monday, a small number of people gathered in the vicinity of the premises involved to express views based on social media comment about the investigation, police said.
District Commander, Chief Inspector Jon Carter, said: “While they are entitled to their views, we would urge the public to allow our highly skilled officers to continue with the investigation.”
He said investigations were ongoing to examine and identify the tablets, and determine exactly how they came to be in the food.
“In the meantime, we have taken protective measures by enforcing a closure of the takeaway,” he said.
“We are continuing to work with partners, including the district council, to understand what happened and the motivations of those involved.
“However, there is nothing to suggest that any other food outlets are involved, or that there is any link with any particular section of the wider community.
“Local officers remain present in the area, and anyone with any information relevant to our investigation is encouraged to come forward.”
Anyone with information should call 101, quoting Operation Enzo.