Twelve people have been arrested in a police operation tackling the suspected manufacture and supply of the drug GHB.
More than 100 officers using chainsaws and battering rams raided seven homes in Oswestry and one in Westbury, Shropshire, at about 0900 BST.
Police claim the drug is possibly linked to two deaths in the county and about a dozen cases of illness.
Items seized included substances thought to be drugs or components used in drug-making, police said.
Nine men and three women were arrested on suspicion of possessing drugs or possession with intent to supply.
'Drug of choice'
Det Ch Insp Alan Edwards, from Shropshire CID, said: "The drug (GHB) is made from industrial chemicals which can have serious damaging effects on users and in extreme cases has proved fatal.
"There have been at least two suspected deaths in Shropshire linked to the use of GHB.
"There have also been a number of life-threatening incidents with people being admitted to hospital in a critical condition, but fortunately eventually recovering."
The inquests have yet to be held into the deaths, he said.
Side effects include unconsciousness, convulsions, seizures and vomiting, he added.
GHB had become the "drug of choice" for some people in Shropshire, particularly in the Oswestry area where there has been a significant problem for some years, Mr Edwards said.
It can be bought fairly cheaply and is "more readily available" than hard drugs such as heroin.