A death originally thought to have been caused by an exploding cell phone is now being blamed on a co-worker, who confessed to making up the story after accidentally striking the victim with a drilling vehicle, South Korean police said Friday.

The quarry worker, only identified by his family name Seo, was found dead Wednesday with a melted phone battery in his shirt pocket.

Police and a local doctor who examined his body said a malfunctioning battery may have killed the man.

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However, after preliminary autopsy results suggested damage to Seo's internal organs was too great to be caused by a cell phone explosion, police questioned the colleague who first reported Seo's death, said Min Kang-gi, a detective in Chungju, some 85 miles south of Seoul.

The man, identified only by his surname Kwon, told police that he accidentally killed Seo while backing up a drilling vehicle, acknowledging that the exploding cell phone story was a farce, Min said.

Kwon told investigators after the accident that he moved his vehicle to throw off police, but did not say he set the mobile phone on fire, Min said.

Police said the phone was made by South Korea's LG Electronics Inc., the world's fifth-largest handset maker.

LG said it knew all along that its cell phone was not the killer.

"LG rigorously tests all the products not only for functionality and design, but safety as well," the company said in a statement.