Analysis of a massive opioid seizure earlier this year has returned some alarming results.

Guelph police had seized what they believed to be blue and purple fentanyl back in mid-March.

Three search warrants had turned up about 266 grams of the substance, with a street value of about $80,000. Police say it was the largest such seizure in the service's history.

On Monday, police announced that a Health Canada analysis of the drugs found that about 260 grams of the seized substance was carfentanil, which is about 100 times more potent than fentanyl.

Two Guelph men, 44 and 59, were charged in March with a number of drug, weapon and property offences.

The first is charged with two counts of trafficking a controlled substance, two counts of possession for the purpose of trafficking, possession of a controlled substance, possession of stolen property and various weapons charges.

The second has been charged with possession of a controlled substance and possession for the purpose of trafficking.

In March, police said in a press release that a third had been requested. In Monday’s press release, police said that a woman had also been arrested.