A man has suffered suspected arsenic poisoning after buying what he believed to be a herbal supplement for impotence over the internet.
Police said a 51-year-old man from the West Midlands had been arrested after forensic testing on the tablets found they contained dangerously high levels of arsenic.
Detectives urged anyone who has bought the black tablets, which are being sold as herbal supplements for impotence, to stop taking them and contact police.
West Yorkshire Police said a man from Leeds became ill after buying the tablets over the internet from BMG Herbal Products in Birmingham.
The man had also been taking red and silver tablets, which were not found to contain arsenic.
Detective Sergeant Steve King, of Leeds District CID, said: "As part of our ongoing inquiries we have arrested a 51-year-old man from the West Midlands on suspicion of selling non-medicinal poison. He has been interviewed and released on bail.
"We would urge anyone who has purchased black tablets from BMG Herbal Products, which are being sold as herbal supplements for impotence, to stop taking them, make contact with West Yorkshire Police or West Midlands Police via 101.
"They are also urged to seek immediate medical advice if they are experiencing any adverse symptoms."