A customs official hid the package in a suitcase belonging to a passenger arriving from Hong Kong as a training exercise for sniffer dogs Sunday, but lost track of both drugs and suitcase during the practice session, a spokeswoman for Tokyo customs said.
Customs regulations specify that a training suitcase be used for such exercises, but the official said he had used passengers' suitcases for similar purposes in the past, domestic media reported.
"The dogs have always been able to find it before," NHK quoted him as saying. "I became overconfident that it would work."
Anyone who finds the package should contact Tokyo customs as soon as possible, the spokeswoman said.