Residents of Change Islands say they're seeing evidence of another oil slick, in the area of where the cargo ship Manolis L sank in the mid-1980s.
Reports of surface sheens prompted the coast guard last spring to install neoprene gaskets to plug hull cracks. In July, it lowered a device called a cofferdam to catch leaking oil.
A new cofferdam was installed just days ago, and was reportedly working.
A surveillance flight earlier this week did not detect oil on the surface.
Meanwhile, a Canadian Coast Guard helicopter and the George R. Pearkes investigated the latest report on Friday afternoon, and a spokesperson said there were no signs of oil.
The Liberian-flagged vessel sank after it ran aground in January 1985 on Blow Hard Rock near Change Islands. It went down loaded with more than 500 tonnes of fuel oil and diesel.