Four people from Carlisle have appeared in court charged with supplying heroin.
The appearances follow 16 arrests made during dawn raids in the city over the past 48 hours.
Officers from Cumbria Police made the arrests as part of an operation to trace heroin dealers in the city.
On Tuesday at Eden magistrates, Tracey Abbot, 25, from Warwick Road; Lee Murphy, 29, from Oakleigh Way; 30-year-old Roger Murphy of Borland Avenue and Richard Rogers, 37 from Warwick Road, were all remanded in custody.
Three more men and a woman are due to appear at a later date to face similar charges.
Eight further people are still being questioned.
The police operation began on Monday and continued on Tuesday.
A Cumbria Police spokesman said more than 40 officers had been involved in the intelligence-led operation.