Police in Bristol arrested four people for drug trafficking and seized Ecstacy tablets worth an estimated £120,000 on Wednesday.
Between 30,000 and 40,000 tablets were seized from an address in the St James Barton area of the city.
The four people, three men and a woman aged between 23 and 30, all from Bristol, have not yet been charged.
A police spokesman said: "We are making concerted efforts to cut the drug supply chain to Bristol."
Det Insp Paul Appleton added: "This is another example of us sending a clear message to people who continue to peddle drugs in Bristol - you will be arrested and prosecuted.
"This was an intelligence-led operation and underlines that we need the community to supply us with information so we can continue our battle to rid Bristol of the drugs menace.",