Retailers are on high alert in Sherbrooke, Que., after more than a dozen dirty needles were found in clothing in stores.

Four people have been recently jabbed by used syringes.

Police say they have found 18 used needles in clothing on sale at four different Sherbrooke retailers — Sears, Intersport, Zellers, and Hart Magasin A Rayons.

The syringes were found in the pockets of clothing on hangers. The needles were pointed up and contained small amounts of blood.

In January, Chantal Ladouceur was stuck with a needle hidden in the pocket of a clothing item she was trying on at the Hart department store.

"It's been stressful," Ladouceur said in a French interview. "I haven't been able to sleep or eat since I was stuck. And I still don't know if I've contracted anything."

Sherbrooke police spokesman Martin Carrier said authorities have no clues or tips so far about the needles' origin and are seeking public co-operation for information.

Meanwhile, retailers in the Eastern Townships area have begun upgrading their in-store security.

"We are trying to be more vigilant," said Laure Jermaine, a retail clothing store worker in Sherbrooke. "We are looking at the pants before and after [customers] try it."

Police said they're waiting for blood analysis test results and fingerprints lifted from the syringes in the hopes the evidence will generate leads in their investigation.