Total said surveys taken from the Elgin drilling platform, about 150 miles off the coast of Aberdeen, indicated the leak of natural gas has slowed by one-third of the initial rate of 7 million cubic feet per day.
Scottish authorities had conducted chemical and sediment testing from sites 2 miles from the Elgin platform and found no direct marine contamination from the natural gas leak, the company said. No natural gas is leaking directly into the water.
The French energy company evacuated personnel from the rig in March and has sent a team of engineers to respond to the incident.
The company last week said it started drilling a relief well to control the leak. Meanwhile, preparations are being made to "kill" the well using heavy mud.
The British Department of Energy and Climate Change last week approved Total's plans to drill a relief well at the site. The DECC said it should take around 180 days to drill the well.