Police raided Toyota Motor Corp.'s headquarters and its Tokyo and Nagoya offices on Tuesday following the arrest of a senior American executive on suspicion of drug law violations.
Toyota spokesman Ryo Sakai said the company could not comment on the raids because the investigation is ongoing.
Julie Hamp, 55, Toyota's newly appointed head of public relations and its highest female executive ever, was arrested June 18 on suspicion of importing oxycodone, a narcotic pain killer, into Japan. The drug is tightly controlled in Japan.
Police say the drugs were in a parcel Hamp mailed to herself. Japanese media reports said the drugs were hidden in a package containing jewelry.
Toyota President Akio Toyoda said last Friday that he believes Hamp did not intend to break the law.
It is unclear what police were looking for in the raids, which are common after arrests.
Hamp, who was appointed in April and previously worked for Toyota's US operations, was in the middle of moving her possessions to Japan. She had been living in a Tokyo hotel, where police arrested her.
Toyota, based in Toyota City, had highlighted Hamp's appointment as a sign that it was promoting diversity.
Some worry that Hamp's arrest will be seen as a sign of risks that come with promoting women, or foreigners, setting back women's efforts to rise up the corporate ladder.
Hamp was not available for comment. In Japan, suspects can be held in custody for up to 23 days without formal charges.
Toyoda said the company perhaps should have helped Hamp more in her move.
Although Japanese Toyota officials have been posted abroad, Hamp was the first senior foreign Toyota executive to be fully stationed in Japan.
It is not unheard of for foreigners to be detained in Japan for mailing or bringing in medicine they used at home. Such drugs may be banned in Japan or require special approval.
Before joining Toyota in 2012, Hamp worked for PepsiCo Inc. and General Motors Co.