The mortar shell was discovered by someone with a metal detector near the HMCS Discovery naval base on Deadman's Island Thursday afternoon.
A Vancouver police bomb squad closed off the part of the park around the facility, which was built during World War II.
Police X-rayed the shell, but could not determine whether it was live or not. It has been removed for further analysis.
Police have now left and reopened the park.
Google Map: HMSC Discovery naval base on Deadman's Island in Stanley Park, Vancouver
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