Total is considering sending its own teams into the exclusion zones around the Elgin platform despite fears it could explode.
The company said to get a better understanding of the leak and how to stop it, workers would have to be deployed closer to the installation.
Last night, union bosses raised concerns about anyone venturing into the restricted area around the field.
Willie Wallace, Unite regional officer for offshore workers, said: “The thing I would be concerned about is Total putting anyone on a boat near the platform while there was any chance of an explosion.
“No one should be able to break the exclusion zone if Total is not 100% sure there is absolutely no chance of putting men’s lives at risk.”
Boats are not allowed within a two-mile radius of the platform and a three-mile no-fly zone has also been declared.
Coastguards said last night that the restrictions would remain in place for as long as necessary.
David Hainsworth, health, safety and environment manager at Total, said: “We are looking at what possible measures we can take to improve surveillance.
“At the moment we are keeping out of the exclusion zones but we are getting prepared to see if we can find a way to safely get our engineers on a boat closer to the platform.”
Mr Hainsworth said there was still a steady flow of gas from the G4 well, and two more firefighting vessels had been to the scene to join the pair dispatched on Tuesday.
Total said a visible gas cloud had formed around the rig and was travelling in an easterly direction.
The company also confirmed a sheen of gas condensate remained unchanged on the surface of the water and a flare continued to burn on the platform.
A spokeswoman for Aberdeen Coastguard said last night that it was “vital” the restrictions put in place around the platform were adhered to.
She added: “We still do not know the full extent of the leak.
“There are a number of reasons boats have been stopped from coming within two miles of the platform.
“There is a flare still burning at the moment and the presence of any vessel there could be the cause of ignition as it only takes a small spark of metal.”
It is understood seawater samples taken from just outside the exclusion zone have been laboratory tested and showed no traces of gas.