Environmentalists are hoping to have the results of gas and air samples taken near the Elgin platform by the end of next week.
Greenpeace members returned to Germany yesterday after sailing to the Elgin platform on Monday.
They spent around 12 hours on site gathering data including air and water samples. These have now been sent to independent laboratories and are currently being analysed.
Bjorn Jettka, the press officer for Greenpeace who was on board the ship, said: “We collected a mixture of air and water samples and have sent them off to be tested.
“We expect the first of the results to be back in around four days and we will know more then.
“When we were out there we could see a constant stream off gas coming from the platform.
“This was being released constantly and was very visible from where we were around three miles away.
“We could also see a thick butter-like yellow substance within the sheen which was sitting on the surface.”
Yesterday Total also released the latest results of the aerial surveys which have been carried out over the platform on a daily basis since the leak began.
Oil Spill Response Limited (OSRL) performed the surveys to monitor the presence and the extent of marine pollution following the leak.
The company then sends out a report for each aerial survey which Total is now publishing online. According to the reports the oil slick around the platform has varied significantly in size over the last 12 days.
Last night a Total spokesman said the gas was still leaking steadily on to the platform.