Several police officers and a member of the public were attacked in Derby city centre this morning.
A 26-year-old man has been arrested on suspicion of assault.
Derbyshire police put a cordon up to close the Wardwick outside Turtle Bay to Cheapside following the incident at around 5am.
Derbyshire Police Statement: “The scene was established after several police officers were sprayed with an unknown liquid and experienced side effects from the incident, at around 4.45am today.
"They were taken to hospital as a precaution and have now been discharged.
“Following a thorough joint investigation between police and Derbyshire Fire and Rescue Service, The Wardwick has been reopened and we can confirm that no harmful substances were found in the area and that there is no risk to members of the public.
“Enquiries are on-going as to the source of the liquid and the effects it had on the officers involved.
“There was also a separate incident in The Wardwick at around 3am, outside of the Living Lounge bar, in which two men were punched and a police officer who stepped in to detain the attacker was also punched in the face.
“The men were not injured, and the police officer sustained minor injuries and was taken to hospital for treatment. He and has since been discharged."