The FIA is still investigating Fernando Alonso's mysterious Barcelona testing crash last month.
The Spanish driver is sitting out Melbourne amid ongoing speculation about his medical condition and what caused him to hit the wall on February 22.
"We are working with McLaren and our medical department is still looking at all the information we can find," FIA race director Charlie Whiting told reporters on Thursday.
"We are still talking to McLaren about anything mechanical. Our medical department is talking to people who treated him in hospital and that is really all I can say on that.
"We can't put a timeframe on it," added Whiting.
The leading theories are that Alonso, 33, was either shocked by McLaren-Honda's fledgling electronic systems, or that a pre-existing medical condition caused him to lose consciousness.
Ferrari's Sebastian Vettel said he had no concerns about the cars not being safe enough.
"I think nobody wants to send us on the track when they believe that something is not right," he said on Thursday.
"I think we have far too much of a team spirit, in all of the teams I would say, to let that happen.
"So when the team decides that it's safe to run, it's safe to run."