Jean Germain left a "goodbye letter" before disappearing without a trace, his lawyer Dominique Tricaud told reporters at the opening of the trial.
"The last time I saw him was last week. He said that no one in his family had ever stood accused in court ... He saw it as a sort of dishonour," the lawyer added.
"I am overwhelmed ... This morning he vanished leaving a goodbye letter at his house."
"According to the very initial elements of the inquiry, we're looking at a suicide," said this source.
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Germain, 67, was due to stand trial for his alleged complicity in a corruption case over Chinese "weddings" that took place in Tours between 2007 and 2011.
A member of his staff, Lise Han, stands accused of fraud, collusion and mishandling public funds.
While she was working at the City Hall on tourism issues, she was also allegedly running a private company organising "wedding trips".
The trips did not include a real wedding ceremony but couples travelled long distances for these "romantic wedding" packages and were photographed in wedding attire in stunning locations, including the Tours City Hall.
Although she had officially resigned from her job as head of the organising group, Time Sarl, she is accused of continuing to run the firm while at City Hall, which was in turn subcontracting the work to her firm.
Germain, who has said he was in the dark about the "lies and manipulations" of Han, stood accused of complicity in collusion and misappropriation of public funds.