Toyota's most senior female executive is being questioned in Japan after investigators discovered pain-killing prescription drugs in a parcel sent to her from the US, according to reports.

Julie Hamp was appointed Toyota's chief communications officer three months ago. She was arrested at a hotel in Tokyo where she was staying on suspicion of violating the country’s drug control law, a police spokesman told AFP. She is a US citizen.

Hamp is reportedly being investigated over allegations that she imported oxycodone, an opioid used to relieve pain. The drug is legal in the US with a prescription, but illegal in Japan, according to the Tokyo police.

They quoted Hamp as saying: "I do not believe I had imported drugs."

A spokesman from Toyota said the company had confidence the investigation would reveal that Hamp did not intend to violate the law.