SOMERVILLE, MASS. (WHDH) - Thousands of dead fish that washed up behind Assembly Square in Somerville earlier this week likely died of natural causes, marine officials said.

Photos taken by Douglas McRay Daniels showed a countless number of fish washed up near the commuter rail tracks at Assembly Station.

Water samples taken in the area did not show any problems with oil or hazardous materials, indicating the deaths were not pollution-related, according to the Department of Environmental Protection.

The Division of Marine Fisheries determined that the deaths were likely due to natural causes, such as aggregations for spawning, predator avoidance, localized oxygen depletion, and rising water temperatures.

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