Police are investigating a sex attack on a young American woman visitor in Queenstown public toilets early today.

The woman went into Earl Street public toilets on the corner of Marine Parade about 2am after socialising with friends in the CBD, Detective Grant Miller said.

"Police have conducted an extensive scene examination and are currently reviewing available CCTV footage," Mr Miller said.

They wanted to hear from anyone who was around Marine Parade, lower Church Street and the war memorial park about 2am today.