Transocean crews over the weekend began drilling a relief well off the coast of Nigeria to allow for the proper abandonment of a Chevron Corp. natural gas well that exploded, killed two contractors, sank, and has remained on fire for more than one month.

The relief well is being dug to help siphon off the flow of natural gas which ignited as the well was being dug. Preliminary indicators suggest surface equipment may have been the cause of the fire.

The natural gas rig has since sunk but fire rages above the water.

Chevron has said it is unclear how long it will take the Transocean crews to drill the relief well. Once the well is complete, Chevron crews will cement the original well shut.

The rig was roughly six miles from the Nigerian Coast. Chevron officials stress the explosion and subsequent fire has caused no significant environmental impact.