The FIA believes a welding failure led to a drain cover becoming dislodged and causing Romain Grosjean to crash during Formula 1 Malaysian Grand Prix practice.
Grosjean's right rear tyre failed in spectacular fashion when he made contact with the drain cover, pitching him into a spin and then the barrier during the second session at Sepang.
"One of the drain covers, which measures about half a metre long and 30cm wide and heavy cast metal, came up," FIA F1 race director Charlie Whiting told Autosport.
"There are quite a few of them around the circuit and at this particular place, there are five at intervals on the outside of T12," he said.
"That's a high-G corner with massive load being put through, and what we have found is some of these drains are bolted down and some are welded down.
"Welding is perfectly acceptable.
"I suspect the bolts which have been going into little sort of lugs on the receptacle, which is where the water goes, have probably broken and rather than replace the whole thing, they've thought, we'll weld it down.
"Quite evidently, the welds just gave up. It's as simple as that really. No one saw that coming."
When asked if it was a freak incident, Whiting said: "Yes, that's exactly what it was."
Ahead of Saturday's running, circuit engineers will look at every drain that does not have bolts in and strengthen them.
"I'm not sure how many there are - we've seen a few, but not that many," he said.
"They will grind all the paint away, they will grind the welds back a bit and they will re-weld them.
"That's all we can do. The drains are not the latest technology."
Whiting said more checks were "probably" required "especially leading up to the grand prix".
He added: "If we were coming back, I would want to discuss a further solution.
"We could recommend in this case a more modern drain system.
"I suspect without a grand prix, they will do the best they can with what they have got."
Sepang International Circuit chief executive Dato' Razlan Razali told Autosport he feels the venue has done everything it could to get the circuit up to safety standards.
"We feel we have done the necessary maintenance," he said. "We have a company that looks after our track. We believe they have done a good job.
"It's a concern for us. Safety is the first priority for everybody. It's the first time it has ever happened.
"We do our regular maintenance but even if we go around and lift every single drain up, for us, it's as fixed as it can be.
"The best thing is to improve for tomorrow."
When asked if he was confident the rest of the weekend would be smooth, he said: "It's in everyone's interest that the track is safe and that the last race will go on."