Sarnia, Ontario. - Hundreds of dead fish that washed up on shore in the north end of the St. Clair River is a natural occurrence and not the result of a chemical spill, a government officials say.

Ministry of Natural Resources spokesperson Jolanta Kowalski confirmed that both the MNR and environment ministry were alerted to a massive die-off of gizzard shad fish late last week.

"We think it's a natural occurrence," Kowalski said. "They died off as a result of temperature shock because we had that really warm weekend ... and then it quickly cooled off again."

Kowalski said such die-offs are not unusual but it typically happens in the spring.

Only one species was affected, further supporting the idea it was a natural occurrence, she said.

"There was nothing to indicate that it was man-made."

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