Drug users in Surrey have been warned by police to be aware of a possible "bad batch" of heroin in circulation.
Officers said a number of users had fallen ill and required hospital treatment after being taken into custody at Guildford police station.
Further checks found they had taken heroin prior to being arrested.
Custody standards manager Geoff Phillips said: "There have been a few incidents lately which have required prompt hospitalisation.
"We are keen to make users aware that there may be a bad batch of heroin in circulation which is causing the problem.
"We do not condone drug use but we do have a responsibility to safeguard all members of the community."