Will Norton was driving home from his school graduation when the tornado struck. His father desperately tried to hold on to his son as the Hummer H3 started to flip, but his seatbelt snapped and he went hurtling through the roof of the vehicle.

This morning his aunt, Tracey Presslor, said that the family received confirmation of his death late Friday night. She declined to say more until a later news conference.

The confirmation of Mr Norton's death came as the toll from the savage storm reached 142 people - making this the deadliest year for tornadoes since 1950, based on an assessment of figures from the National Weather Service.

The total tornado death toll for 2011 is now 520. Until now, the highest recorded death toll in a single year was 519 in 1953.

There were deadlier storms before 1950, but those counts were based on estimates and not on precise figures.

Missouri says the number of people still unaccounted for since the Joplin tornado is now at 105. State Department of Public Safety deputy director Andrea Spillars said Saturday that within that number, nine people have been reported dead by their families.

She said that the temporary morgue has 142 human remains, but that includes partial remains.

'Some of those remains may be the same person,' she said, adding that officials are trying to use scientific means rather than relying on relatives giving visual identifications.

Identification of the deceased has been slow because officials have taken extra precautions since a woman misidentified one victim as her son in the chaotic hours after the tornado hit.

Authorities say their deliberate efforts on identifying the bodies are necessary to avoid more mishaps. Read More