A mystery is brewing at universities across Canada.

Unexplained packages from Amazon are arriving at student union offices – and now both Amazon and the RCMP are investigating.

Here in Quebec, student associations at both Concordia and Bishop's universities have been receiving these packages for months.

There's never a regular frequency - sometimes they'll go weeks without one only to get five in one day.

The packages are full of all kinds of items, including phone chargers, filament for 3D printers, lamps, batteries and even in some cases sex toys.

Every package has an anonymous sender, making it difficult for these student groups to track their origin.

The student association at Bishops told CTV News all of their packages are arriving from China, and Concordia said according to the receipts that come with the boxes, most of items were bought with gift cards.

At least 15 universities across the country have also received Amazon boxes.

Students at Lakehead University in Thunder Bay were receiving so many, they called the RCMP. Police have now launched an investigation there.

“We heard about other universities getting them this week, which was pretty funny to know we weren't the only ones in this mystery but it's very puzzling,” said CSU student life coordinator Leyla Sutherland. “The assortment of items doesn't make sense. Why student unions?”

“We received one thing, then a couple of days later, we received two, and it being before Christmas we thought maybe someone is doing a 12 Days of Christmas prank on us, but then it became obvious that wasn't the situation. Since then we've gotten over 50 by now,” said Erin Mallory, GM administration students’ representative council at Bishop’s.

Amazon is also investigating.

Many student groups, including the one at Concordia have reported these packages to the company.

Amazon said in a statement: "We are investigating inquiries from consumers who have received unsolicited packages as this would violate our policies. We have confirmed the sellers involved did not receive names or shipping addresses from Amazon."

For now, the student groups have been giving them away; at Bishop's, the student association is keeping all its items as prizes for its pub quiz night.