An investigation is under way after a woman reported being injected with an unknown substance in Preston at the weekend.
Police were also called to a separate incident in the city on Saturday where two women reported having their drinks spiked, the force said.
A Lancashire Police spokesman said officers were called on Sunday after a woman in her late teens attended hospital with concerns she had been injected.
The incident is believed to have taken place in Preston city centre some time between 10.20pm on Saturday and 4.45am.
Just before midnight on Saturday, police were called to Lancaster Road by the ambulance service after reports two women, one in her 20s and the other in her 30s, had their drinks spiked.
Both women were taken to hospital but later discharged, the force said.
Police said the two incidents were not being treated as linked but officers were keeping an open mind.
The reports came amid a rise in reports of drink spiking and claims people have been drugged by injection.
Detective Inspector George Binns said: “We appreciate that there is a great deal of concern surrounding these reports, particularly on the back of what has been reported elsewhere in the country.
“We take reports like these extremely seriously and are working diligently to get to the bottom of exactly what has happened.
“We are at the early stages of our investigations and we will update the public further as soon as we can.
“The victims are being supported and I would encourage anybody with information which could assist our inquiries to come forward.
“If you think you have been the victim of this kind of offence, we would encourage you to report it to the police or a member of the bar staff as soon as possible.
“You will be believed and it will allow us to obtain the strongest possible evidence to secure a conviction.”
He said police were liaising with licensing and venues about safety and there would be “reassurance patrols” in Preston next weekend.
Anyone with information should call 101, quoting log 1108 of October 24 2021.