The ongoing North Sea gas leak at Total's Elgin platform has not directly contaminated the marine environment, the Scottish government said on Wednesday citing the results of tests of water and sediment.

All data gathered to date continues to demonstrate that the effects on the marine environment of the Elgin gas leak are, so far, minimal, Scottish Environment Secretary Richard Lochhead said in a statement.

Samples collected on the edge of a two-mile exclusion zone around the evacuated platform found no traces of oil and gas pollution, the government said.

The government said traces of oil-based hydrocarbons that were found in seawater samples were likely the result of other shipping or industrial activities in the area.

The sediment samples were found to be unaffected by the gas leak, with the samples' chemical indicators being typical of what is found elsewhere in the North Sea, it said.

Total plans to plug the leak with a so-called well kill by pumping heavy mud into the pipe.

Another, more expensive option being pursued in parallel is to dig two relief wells to the source of the gas at 4,000 metres depth, far below the sea bed.

The gas leak was reported on March 25 and is spewing an estimated 200,000 cubic metres of natural gas into the air per day, forming a highly explosive gas cloud around the platform.

(Reporting by Oleg Vukmanovic; editing by Jason Neely)