FRANKFURT  Adolf Merckle, the German billionaire whose speculation in volatile Volkswagen stock had pushed his sprawling business empire to the edge of ruin, has committed suicide, his family said Tuesday.

Mr. Merckle, 74, was found dead on railroad tracks near his villa in the southern German hamlet of Blaubeuren on Monday evening. German authorities in the nearby city of Ulm confirmed the death and said there was no sign anyone else was involved.

“The distress to his firms caused by the financial crisis and the related uncertainties of recent weeks, along with the helplessness of no longer being able to handle the situation, broke the passionate family businessman, and he ended his life,” the family said in a statement.

The police said a suicide note had been found; its contents were not publicly released.

More than any other single investment, Mr. Merckle’s poorly timed bet on Volkswagen shares caused the financial distress that led to his death.