Chief among them is a belief that the Spaniard was knocked unconscious by an electric shock from his McLaren-Honda's powerful on-board batteries, which help power the car.

It has been reported that unidentified teams are so concerned about the possibility that his crash was caused by an extreme malfunction of the hybrid power unit's high-voltage electrical system — variations of which all the teams use — that they have threatened to boycott the Australian GP unless its failure is ruled out.

But as suspicions and fears grow about the unexplained cause of the accident, which resulted in the two-time world champion suffering severe concussion, a F1 technical expert has dimsissed electrocution as a possible cause.

The top-level engineer told Fairfax Media on condition of anonymity that the high-voltage electrical systems of F1 cars were heavily shielded and further protected by fail-safe systems.

According to the expert, who has worked on battery-powered booster systems since they were first introduced in F1 in 2009, the systems are designed to automatically shut down if overloaded.

His conviction that Alonso wasn't rendered unconscious just before the crash by an electric shock is based on the all-or-nothing nature of the batteries' output, which is estimated at 400-600 volts, in the unlikely event of an aberrant discharge that somehow defeated all the safeguards.

"He could not get a small shock," the expert said. "He'd either get a life-threatening shock or none at all."

Since last year, all F1 cars have had dual energy recovery systems that harvest waste heat energy from the brakes and engine turbocharger, converting it to electricity that is stored in batteries.

The stored energy is released on demand to assist the turbocharged 1.6-litre V6 engine, temporarily boosting power to around a total of 750 horsepower.

Speculation about the cause of Alonso's crash has intensified despite the strenuous denials of the McLaren-Honda team that his car suffered any catastrophic failure.

The mystery has deepened following reports that Alonso suffered a major memory loss immediately after the accident, along with suggestions that his concussion was more serious than portrayed.

Although he is due to return at the Malaysian GP in three weeks, fears have been expressed that Alonso may not be able to race again because of the risk of a more severe head injury if he were to be involved in another high-impact crash.

Alonso, 33, was due to make his racing return with the renewed McLaren-Honda partnership at Albert Park after five years with Ferrari. He drove for McLaren in 2007 after winning back-to-back F1 world championships with Renault, but left after just a season after falling out with team boss Ron Dennis.

He went back to Renault for two years before joining Ferrari, where he was runner-up thrice.