The Coast Guard continues to investigate the wreck of the tank barge Argo in Lake Erie near Kelley’s Island, Ohio.

A pinhole-sized leak in one of the vessel’s cargo tanks was discovered and plugged last week. Divers planned to unseal that plug on Monday to collect a sample of the product inside for identification.

Results from a sheen sample collected earlier in the investigation indicated a light to medium refined oil that had significantly degraded over time. The Argo sunk during a storm in 1937 and was discovered in August. There are no detailed records of the ship's cargo, but she was believed to be carrying crude oil and benzol — estimated to be about 100,000 gals. of each.

The Coast Guard has been working with T&T Marine Salvage on the investigation. T&T crews completed their general assessment of the barge last week, finding a total of 12 hatches, according to the Coast Guard. Four hatches were not secured, the Coast Guard said, and the remaining eight were closed with no leaks detected. Samples taken from the sediment inside the open departments were inconclusive.

As a precaution while investigation and testing continues, the Coast Guard has extended the safety zone to a full nautical mile radius directly above the barge’s location. No vessel may enter, transit through, or anchor within the regulated area without permission from the Coast Guard patrol commander, Station Marblehead.