Merseyside Police have confirmed three further people were taken to hospital on Monday night after it is thought they took a substance known as GEEBS.
Emergency services were called to student accommodation at Hatton Garden, Liverpool city centre at around 5.15pm.
Two men, both aged 20 years were taken to the Royal Liverpool University Hospital by ambulance, where they received treatment prior to being discharged.
A third man, a 19 year old from Mold, was also taken to hospital.
It is believed he took the substance with the other two men. He has also now been discharged.
A 20-year-old man from the Liverpool area has been arrested on suspicion of possession with intent to supply a controlled drug.
He was taken to a police station on Merseyside where he remains at this time.
He will be questioned by detectives today.
The accommodation at Hatton Garden has been secured for examination and detectives continue to make enquiries with other residents.
At this stage of the investigation it is unclear where the men had been prior to emergency services being contacted and if this incident is linked to a previous incident at Bordens Court where three other people were taken ill on Sunday.
Detectives Superintendent Chris Green, said: "This latest incident shows how important it is to listen to our warning about the effects this substance can have.
"Thankfully these men have not suffered serious effects, however I would like to re-iterate my warning to students and young people that if taken, GEEBS, which is actually a chemical used to clean alloy wheels, can have serious side effects and can kill, even in small doses.
"We will continue to work with our city's universities to warn people about the dangers of taking drugs and chemicals, particularly if mixed with alcohol, or other substances."
Anyone with any information about this incident is asked to contact 0151 777 4064 or Crimestoppers anonymously on 0800 555 111.