London ? Their naked corpses showed no signs of struggle, raising questions of whether a suspected serial killer may have drugged the five young women – all addicts and prostitutes – before killing them and dumping their bodies on the outskirts of an English port town.

“The fact that they were drug users will make the work more complicated” for forensic experts, said Sandra Graffham, a Suffolk police spokeswoman.

The fifth victim was identified Friday as Annette Nicholls, 29, but a coroner was unable to say what caused her death.

One woman died from asphyxiation and another died from what a coroner called “compression to the neck.” The causes of death for two others are still unclear because their bodies were found in water.

Forensic psychologists have asked whether the killer lured and then anesthetized the women with drugs. None of the bodies showed signs of significant trauma or sexual assault. However, it will take days to complete toxicology reports that could show whether the women had been drugged or the level of previous drug use, police said.

Experts from Britain’s equivalent of the FBI – the National Centre for Policing Excellence – were in Ipswich, a town about 70 miles northeast of London that used to be a bustling port in the 19th century. About 300 specialists have also been sent in.

A woman lights a candle Friday near a montage of the five young prostitutes, Gemma Adams, Tania Nicol, Annette Nicholls, Paula Clennell and Anneli Alderton, whose bodies were discovered in and near Ipswich, England. A remembrance service was Friday in a Copdock, England, church.

Kevin Dominic Browne, who specializes in forensic psychology and whose center in Birmingham has studied serial killers, said the killer may have drugged his victims to ensure he had power over them.

He said often these types of killers have been abused themselves or suffered some type of trauma associated with sexual intimacy.

Serial killers usually enjoy the physical sensation of killing, preferring strangulation or bludgeoning to guns and other weapons, experts said.

“It may be this person gets a real charge out of playing God but doesn’t necessarily relish hearing the screams of his victims,” said James Alan Fox, a psychology professor at Northeastern University in Boston and author of several books on serial killers. “Drugging them would have also made it easier on him – psychologically – to abduct them, kill them and dispose of their bodies.”