Organization president Akio Toyoda said at a news meeting that US national Julie Hamp had not planned to transgress against the law.
Ms Hamp serves as Toyota's head of advertising and is its first senior lady official.
She is blamed for sending herself 57 tablets of the painkiller oxycodone in a bundle checked "neckbands".
Mr Toyoda said the organization ought to have accomplished more to help Ms Hamp, who was presently migrating to Japan.
He portrayed her as "a dear partner whom I trust" and included: "We trust it will turn out to be clear that Ms Hamp did not expect to overstep the law."
The organization has said it will completely co-work with the examination.
Ms Hamp told police she didn't think she had imported an unlawful substance, as indicated by a representative for Tokyo's Metropolitan Police Department.
Oxycodone is a legitimate substance in the US and Japan, however it must be imported into Japan on the off chance that it is conveyed by a man who has a true blue medicine.
Ms Hamp, 55, was named correspondences boss in April as a major aspect of a drive to differentiate Toyota's male-ruled, basically Japanese official line-up.
She joined Toyota's North American unit in 2012 having beforehand been an official at General Motors and PepsiCo.
