A popular lake in Timmins is seeing dead fish wash up on its shores in large numbers and officials say rising temperatures are likely the cause.

The Mattagami Regional Conservation Authority said workers were disposing of dead fish from Gillies Lake by the bucketful.

Some residents noticed more than 100 dead fish washed-up along the shoreline and took to social media wondering why there are so many around Gillies.

The Ontario Ministry of Natural Resources and Forestry investigated.

"Samples of the dead fish that were collected showed no sign of water contamination or disease. So, based on the evidence available, this mortality was likely stress-related, caused by low oxygen levels and higher water temperatures," Karen Passmore, of the MNRF.

'Winter kill' is a phenomena that's been known to kill fish in similar lakes in Regina as well, due to freezing ice sealing the lake from oxygen in the air.

But Passmore says 'summer kill' also affects lake ecosystems. She says it hasn't happened to Gillies Lake in recent memory, but it's not unusual in Ontario.

The Ministry of Environment, Conservation and Parks also responded to make sure no accidental chemical contamination caused the situation.

"In this case, we sent out an officer to verify that and it was confirmed that there is no visual signs of a spill at the site," said George Lajeunesse, of Ministry of Environment, Conservation and Parks.

Passmore says it depends on the type of fish, but smaller ones and tadpoles tend to survive these conditions just fine, it's generally larger species that have more trouble with depleted oxygen.