TOKYO (Reuters) - Toyota Motor Corp’s head of public relations, an American and its first female senior executive, was arrested on Thursday on a suspected violation of Japan’s drug laws for sending a painkiller through the mail.

Julie Hamp, an American appointed in April as the carmaker’s chief communications officer, its first female managing officer, was arrested after the painkiller Oxycodone was mailed from the United States to Tokyo’s Narita Airport, Tokyo police said.

Hamp said she did not think she had imported an illegal substance, a spokesman for Tokyo’s Metropolitan Police Department said, while Toyota stood by the Tokyo-based executive.

“Toyota has been made aware of Ms. Hamp’s arrest but has no further facts in light of the ongoing investigation by the authorities,” Toyota spokesman Shino Yamada said in an emailed statement.

“We will continue to cooperate fully with the investigation. We are confident, however, that once the investigation is complete, it will be revealed that there was no intention on Ms. Hamp’s part to violate any law.”

Oxycodone, an addictive painkiller, is a prescription drug in the United States. In Japan, the police said, only specially designated parties were allowed to import the drug.

Hamp’s promotion in April, along with the appointment of Toyota Europe chief Didier Leroy as executive vice president and African-American Christopher Reynolds as a managing officer, marked the acceleration of a diversification drive for a management team long dominated by Japanese men.

Prime Minister Shinzo Abe has called on corporate Japan to appoint women to 30 percent of top jobs by 2020. Women account for only 11 percent of mid- to senior-level management jobs in Japan and 1 percent of executive committee members, according to researcher McKinsey.