A man from Trowbridge has been arrested on suspicion of possession with intent to supply class A drugs.
The 17-year-old remains in Melksham custody on Sunday morning for questioning.
It follows a warning from police to people in Trowbridge and Westbury regarding a potentially rogue batch of contaminated MDMA.
Two teenage girls suffered a bad reaction on Saturday evening to drugs they had been sold in Westbury earlier.
Obviously our message is always the same - steer well clear of any illegal drug use. However, we have concerns that there may be a dodgy batch of MDMA in our community which could lead to further illness.