A bomb disposal team was called to deal with highly explosive chemicals after a "drugs lab" was found in Kent.
The UK Anti-Doping Agency (UKAD) said large quantities of steroids and DNP - a toxic fat-burning drug illegal for human consumption - were discovered at a unit in Queenborough, on Sheppey.
After raids in Kent and Oxfordshire, UKAD director of operations Pat Myhill said it was "an established operation".
Two men were arrested and released while inquiries continue.
A Sittingbourne property was also searched.
The raids were carried out by the Eastern Region Special Operations Unit, Kent Police, the Medicines and Healthcare Products Regulatory Agency, the Food Standards Agency and UKAD.
