A shop in Northampton town centre was raided by police as part of a crackdown on legal highs.
Officers seized a number of substances, along with a quantity of cannabis. One person received a police caution.
Police have stepped up patrols around shops known to be selling legal highs in a bid, they say, to tackle the “associated anti-social behaviour that takes place nearby”.
Town centre sergeant, Simon Pinchin, said: ““The issue of legal highs is now a big issue for town centre policing and is taking up a disproportionate amount of our time.
“It would appear that some shopkeepers see easy pickings from their sale and the huge profits they generate.
“There were 68 fatalities from legal highs in the UK in 2012, and my feeling is that it’s only a matter of time before somebody gets seriously ill from ingesting them in Northampton.
“I urge people to take notice - they carry serious health risks; the chemicals they contain have in most cases never been used in drugs for human consumption and haven’t been safety tested.
“Users can never be certain what they are taking and what the effects might be.”