The Rape Crisis Centre in Belfast has dealt with ten cases in the last six months - five of which involved the well known date rape drug Rohypnol.

Rohypnol is a tasteless, colourless and odourless substance but manufacturers have recently introduced a blue dye into it, to colour any liquid into which it is placed.

When slipped into a drink the powerful sedatives can take affect within minutes, causing dizziness, drowsiness and confusion lasting for up to eight hours.

The Rape Crisis Centre has dealt with drug rape cases in Bangor, Carrickfergus, Rathcoole, Newry and Belfast.

Spokeswoman Eileen Calder says it is a big problem across Northern Ireland.

"It is a big problem now and I think the vast majority of victims probably don't report," she said.

"At the end of the day I think its almost impossible to drink safely now in a nightclub unless you hold onto your drink permanently and don't accept a drink from anybody that you don't know."

Victims reluctant to report crime

She said that victims of drug-induced rape were less likely to report the attack than other sexual assaults.

"The victims find it hard to believe themselves and they certainly don't think anyone else will believe their story," she said.

"One woman didn't realise she had been raped until eight weeks later when she discovered she was pregnant."

Date rape drugs have been a phenomenon in the United States and even England in the past, but to date not in Northern Ireland.

In the mid 1990s the US Congress passed the Drug Induced Rape Prevention and Punishment Act which provided a maximum sentence of 20 years for anyone using drugs to carry out a sexual assault.