British police have arrested two men and three women and searched four UK properties in an investigation into insider dealing.
The arrests come as financial watchdogs attempt to crack down on market abuse.
The Financial Services Authority (FSA) said that the two men, aged 37 and 62, and three women, aged 39, 51 and 63, were in custody and were awaiting questioning by police.
No further details were immediately available, though the regulator said the arrests were not linked to any other ongoing insider dealing investigation.
Britain's financial regulator is currently prosecuting six other individuals for insider dealing and has so far secured 21 convictions for the offence, which can carry a jail sentence of up to seven years.