An Uber driver in California claims that a customer of the ride-sharing app had him deliver fentanyl instead of a passanger, authorities said.

The driver was attempting to pick up a female passenger in San Francisco last week, to be driven to Tiburon, a town roughly 17 miles north of the city, when a man greeted him instead, the Marin County Sheriff's Office wrote in a Facebook post on Saturday.

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The man told the driver he didn't need a ride but wanted him to "deliver a box to the woman that requested the ride."

Officials said the driver was "hesitant" to fulfill that request, but "since the man knew the name of the person who requested the ride, he agreed to do it."

The Uber driver put the sneaker box on the floor near the passenger's seat and headed to the location. Suddenly, as he was crossing the Golden Gate Bridge, the woman canceled the ride, leaving the driver with the mysterious shoebox.

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Officials said that minutes later, the driver spotted Marin County sheriff's deputies and asked for their help to examine the box. The deputies found a pair of Nike sneakers inside, with "suspected fentanyl in the right shoe."

Authorities took the sneakers into evidence — "since the driver wanted nothing to do with the shoes or drugs" — and joked they will be "waiting for the owner to claim them."