A Tokyo investigator in the high-profile case of missing Briton Lucie Blackman has dismissed criticism that police have detained the wrong man in trying to discover her whereabouts.

"We have seized a number of videotapes that were privately taken by Joji Obara showing him committing obscene acts with more than 50 women," the investigator said. Even if Obara has nothing to do with the Blackman case, he said, these other cases "are worth investigating."

But this will not alleviate the frustration that police -- under pressure to find her from various quarters, including British Prime Minister Tony Blair -- are encountering.