Tourists walk past the Happy Special Pizza restaurant, where several individuals were arrested during a drug bust on Tuesday in Siem Reap town. Photograph: Thik Kaliyann/Phnom Penh Post

Drug raids at a “happy” pizza restaurant and a “psychedelic” guesthouse in Siem Reap on Tuesday resulted in 21 people being arrested, including 17 tourists from countries including the US, France, Canada, Germany and Australia.

The crackdown started early on Tuesday morning, when police arrested three New Zealand tourists along with a pair of tuk-tuk drivers at Happy Pizza Restaurant in Svay Dangkum commune on the accusation of using illegal substances and drug distribution.

Siem Reap town police chief Mok Aun said officers uncovered a kilogram of a “dried narcotic plant” as well as a second substance from the suspects, including pipes from the suspects, who he said were smoking when police arrived.

“These three New Zealand tourists and two Cambodians had publicly smoked the marijuana at the Happy Special Pizza Restaurant,” he said.

“They were arrested by our police while they were smoking the marijuana. They were accused of drug distributing and use.

“They are now being questioned about their drug-distributing activities by the provincial anti-drugs police in Siem Reap province. If enough evidence is found, they will be sent to court for charges,” he added.

Siem Reap provincial deputy prosector Chhun Sophanha confirmed yesterday that the restaurant’s owners were also taken in for questioning.

“Police arrested three tourists and two Khmer people and then we decided to detain the owners,” he said.

Following the raid at Happy Pizza, one of the arrested tuk-tuk drivers told police  the Villa Anjuna guesthouse in Sala Kamroeuk commune – which the owners dubbed a slice of “trance culture” in a 2011 Post story – was often the destination for drug deliveries. Siem Riep deputy police chief Um Amra said a raid on the guesthouse was ordered, where another 14 individuals, all foreigners, were scooped up.

Italy and Switzerland round out the roster of nationalities of those now being held at Siem Reap provincial police station.

No date has been announced for court appearances.