Eight police officers had to be treated in hospital after being exposed to an unknown substance during a house raid.
The officers, from the West Midlands Police force, were carrying out a search at a house in the Bordesley Green area of Birmingham at around 00.00 (31 August).
Three men, aged 21, 27 and 34, were arrested on suspicion of conspiracy to possess a controlled drug with intent to supply.
Police say they also seized a "very large" quantity of suspected Class A drugs with an approximate street value of around £250,000.
During the raid, officers were exposed to an unknown substance, which caused ill-effects for both the officers and the people arrested, namely sickness and breathing difficulties.
Eight police officers and the three people arrested were taken to Heartlands Hospital.
All were discharged this morning.