Staff at a Toronto apiary say they're heartbroken after thousands of bees died of exposure after vandals damaged several hives and stole honey.

The Fort York organization, which runs the apiary at the historic site, tweeted the news on Friday.

The organization said Toronto Honeys, a local urban beekeeping group, is "working to save some bees from the damaged hives."

We're heartbroken: our apiary was vandalized and bees have died due to exposure. If you see anything please call police at (416) 808-1400 <a href="https://t.co/hoOp80wlvD">pic.twitter.com/hoOp80wlvD</a> —@fortyork

Shawn Caza, a beekeeper with Toronto Honeys, said he first noticed possible tampering with the hives back at the beginning in December.

Closer to Christmas, he came back to do a final check, and noticed some honey had been cut out of different hives. He says it's not clear when it happened.

Bee update: the 4 hives left are safe. <a href="https://twitter.com/TorontoHoneys">@TorontoHoneys</a> are working to save some bees from the damaged hives. Thank you for your support 🐝💛 <a href="https://t.co/FBbG91A175">pic.twitter.com/FBbG91A175</a> —@fortyork

Then, on Thursday, he returned to an even worse scene: Every single hive had a protective cloth peeled off, honey was removed, and in three hives there was no bee movement.

"Our strongest hive that was just full of bees is one of the ones that died," he said.

Less than a fifth of bees left

The total bee population prior to the damage was about 20,000 or 30,000 bees, Caza said. Now, less than a fifth is thought to be left.

Six to eight frames of four pounds of honey each appeared to be stolen, he added.

"It's really strange," said fellow beekeeper Melissa Berney.

It's been a bit of a sad time for us. I'm exhausted from trying to sort out the mess. Looking forward to brighter times. <a href="https://t.co/bYfhJhPvGb">https://t.co/bYfhJhPvGb</a> —@TorontoHoneys

Fort York has been working with Toronto Honeys for four years, according to the historic site's manager, David O'Hara. He estimates 500 to 600 pounds of honey have been produced so far.

"It's a program that's been quite successful," he said.

The area, he added, is secured at night.

O'Hara said Fort York has plans to contact the police.