The American authorities have failed to find a causal relation between a controversial car fire in Florida on Sept. 5 and its owner's Galaxy Note 7, a US newspaper reported on Monday, in the latest development that may vindicate Samsung Electronics' position in its ongoing global recall of the smartphones.

According to the US media report, the exact cause of the Sept. 5 fire that ripped through a car with a Galaxy Note 7 smartphone reportedly being left inside in St. Petersburg, a southeastern city of Florida, has been classified as unknown after an investigation by the US firefight authorities.

Citing an e-mail to media sent by St. Petersburg Fire Rescue, The St. Pete Patch reported on its website that the outcome of the investigation "cannot isolate a Samsung Galaxy Note 7 that was reportedly left in the vehicle as the ignition source."

The family of the car reportedly blamed the Note 7 for the car fire as Samsung is recalling the latest smartphone over a faulty battery.

"It was reported that a Samsung Galaxy Note 7 was in the vehicle at the time of the fire and there were allegations that it may have been the cause," the report quoted St. Petersburg Fire Rescue as saying.

"After a thorough investigation, fire investigators did not find a cause for the fire," it said.

At this stage, the fire was caused by an "undetermined" factor, it said.

"Due to the destructive nature of the fire, and multiple possibilities that could not be eliminated as to the ignition source, this classification was determined most appropriate," the report quoted St. Petersburg Fire Rescue as saying.

As part of its global replacement program, Samsung plans to exchange about 1 million Galaxy Note 7s sold in the US for new ones starting on Sept. 21, according to company officials.

The replacement program was launched in South Korea on Monday, about two weeks after the world's largest maker of smartphones announced the global recall. (Yonhap)