Visitors were searched at the weekend in a surprise operation that used drug-sniffer dogs, police and specially-trained security officers.

Police allegedly seized 1.5grams of white powder, 0.8grams of ice, two grams of cannabis, 14 tablets, knives, 3.7litres of alcohol, syringes and smoking devices.

The contraband was allegedly found in vehicles and peoples’ possession.

A Corrective Services Department spokesman said searches were done in the jail car park as visitors arrived.

“While the majority of visitors do the right thing and abide by the law, there are always concerns some may think they can get items such as alcohol, cash and drugs into correctional centres,’’ the spokesman said.

“Our vigilance is having an effect.’’

About 340 visitors to the jail were lined up to face drug-sniffer dogs.

The spokesman said 180 vehicles were searched.

Seventeen people were denied entry to the jail and 16 people charged.

The spokesman said those who were charged faced bans from all NSW jails.

The bans could vary from months to years depending on the charges and Corrective Services Commissioner Ron Woodham’s assessment of each case.

The two-day sting was a joint police and Corrective Services operation that started at 8am on Saturday and finished at 4pm yesterday.

It was part of a larger operation over a few months that included state prisons at Kempsey, Muswellbrook, Tamworth, Grafton, Oberon and Glen Innes.

‘‘These operations will continue in a concerted effort to reduce contraband that is trafficked into correctional centres,’’ the spokesman said.

Corrective Services data shows that Cessnock prison, which houses minimum and maximum-security prisoners, expanded from 347 inmates in June 2010 to 462 in June last year.