text: The dress, studded with 6,000 natural white pearls, was taken from the London Hotel in West Hollywood while Nyong'o was out of the room.
  Nyong'o won best supporting actress in 2014 for 12 Years a Slave and was a presenter at Sunday's ceremony.
  A statement from the hotel said they were "working with law enforcement".
  Lieutenant William Nash, of the Los Angeles County Sheriff's Department, said officers were checking CCTV footage.
  Conflicting reports suggested the dress was stolen either on Tuesday night or during the day on Wednesday.
  "Ms Nyong'o was not in the room at the time of the theft," Deputy John Mitchell told Reuters.
  'Homage'
  The dress, designed by Francisco Costa for Calvin Klein, took 25 people 10 weeks to hand-sew the 6,000 Akoya pearls.
  On the red carpet on Sunday, the actress told Associated Press she was "just wearing my diamonds and pearls. My homage to (musician) Prince".
  Speaking about the dress's design, the 31-year-old said: "We talked about it being fluid and liquid. I wanted it to be an homage to the sea."
  No arrests have been made.
  Representatives for Calvin Klein declined to comment.
target: A $150,000 (Â£97,000) custom-made Calvin Klein dress, worn by actress Lupita Nyong'o at this year's Oscars, has been stolen in Hollywood.