LONDON (AP) — A British chef was convicted Wednesday of murdering three young men whom he met online, plied with lethal drug-spiked drinks and raped, before leaving their bodies in and around a graveyard near his home.

Jurors found serial killer Stephen Port guilty of three murders and more than a dozen additional offenses, including rape and sexual assault, involving several other men.

Port, 41, denied all the charges against him.

The U.K.'s independent police watchdog is investigating why detectives did not initially link the deaths of the three men whose bodies were found near Port's home in east London over a 15-month period.

Prosecutors said Port invited the men, who all were in their 20s, to his home, where he gave them drinks containing deadly doses of the psychoactive drug GHB so he could rape them while they were unconscious.

The men — Gabriel Kovari, Daniel Whitworth and Jack Taylor — all overdosed on the drug. Port then dumped their bodies in and around a graveyard near his apartment.

He took elaborate action to cover up the killings, planting a fake suicide note in the hand of one victim and stashing drugs on the body of another.

Police only began investigating the deaths as potential homicides when the family of Port's final victim, Taylor, pressed for action.

But jurors at London's Central Criminal Court convicted him of the murders and a range of other offenses that included three rapes and three sexual assaults of men who survived their encounters with Port.

Jurors are still deliberating on one other murder charge.