The Kardashian clan has a series of reality shows on E!, but the network said Tuesday it did not have cameras at the stadium to capture the moment.
Representatives for West, 36, and Kardashian didn't immediately respond to emails seeking comment about the engagement.
A photo posted on Instagram shows a screen at the stadium that reads "PLEEEASE MARRY MEEE!!!" - in typical West font - above a black-clad orchestra. Another shows Kardashian showing off a diamond ring with a smiling West behind her.
Khloe Kardashian seemed to celebrate on Twitter when she wrote: "Tears of JOY!!!!!!! Wow!!!!!!" She also tweeted: "Wow!!!!! Am I dreaming??!?!" Kimye were quiet on Twitter.
Kardashian was previously married to NBA player Kris Humphries. Their divorce was finalized in June after they were married for 72 days in 2011.
West is currently on a tour with Kendrick Lamar. "The Yeezus Tour" will visit the SAP Center in San Jose on Tuesday night. Earlier Monday, he attended the Hollywood Film Awards in Beverly Hills, presenting Steve McQueen with the Hollywood Breakout Director Award.
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