Humberside Police say there has been a confirmed incident of spiking by injection in Hull, with another report that is being assessed.
They want to highlight that both incidents are being treated extremely seriously and investigations are progressing.
Members of the public will continue to see police officers in both plain clothes and high visibility uniform patrolling areas which are busy nightlife hot spots. Officers are reminding people about the 'Ask for Angela' scheme where if they are concerned they can approach a member of staff and ask for ‘Angela’. They will then take that person to a place of safety.
The signs to look out for include anyone acting or behaving suspiciously with another person who looks too intoxicated or who has been separated from friends, anyone trying to get someone out on their own or anyone leading someone into a taxi or unmarked car.
Detective Chief Inspector Pete Thorp said: “We understand that hearing of incidents of this nature in this area can be concerning for the public and we would urge everyone to continue to remain vigilant."
Tips on spiking can be found on the Talk to Frank website.