Preliminary lab results show that hundreds of dead fish reported at a west metro lake may have died as the result of a common fish disease. But more tests are being done to rule out any other causes.

Boaters flocking to Lake Independence near Maple Plain over the Memorial Day weekend found an estimated 500 to 1,000 dead fish washed ashore. One parks worker relayed a resident’s complaint that they could “walk across the water on top of the fish, they were so thick,” according to a University of Minnesota report.

Veterinary students investigated the incident for the state Department of Natural Resources, testing the dead fish — black crappies, sunfish and perch, all 4 to 6 inches long — and the water quality. They found mild columnaris disease, a common fish disease that can occur when water temperatures warm in the spring.

However, according to the report, it’s unclear if the disease was the primary or secondary cause of death. The dead fish since have been removed from the lake.