A number of suspected drink-spiking incidents, which resulted in several people being taken to hospital, are being investigated by police.
Drinkers from Pembrokeshire College and the nearby Glen Hotel in Haverfordwest had to be treated after falling ill.
An appeal has been made for anyone feeling ill after drinking at the two venues on Wednesday to contact their doctor immediately.
Dyfed-Powys Police said a man and a woman were being questioned.
A spokesman said: "Dyfed-Powys Police are investigating a number of incidents in which drinks have been spiked in and around the Glen Hotel, Merlins Hill, Haverfordwest and Pembrokeshire College in Haverfordwest.
"As a result a number of people have complained of feeling unwell and have been treated in hospital.
"One is still receiving treatment in hospital.
"Incidents such as this are very rare and the police believe that these incidents are contained to this area and two people are currently assisting police with their inquiries."
A substance has been sent to experts by detectives for testing.
Anyone who has any information should contact the police on 0845 330 2000.