Reader, I was there!
There was a loud banging and clanging. The orchestra stopped playing. Rene Pape turned toward the audience (perhaps speaking to the prompter?), and said “Curtain.” Awkward pause. “Curtain.” (He might have actually said “Close the curtain.”) The curtain did, indeed, close. A cryptic announcement came on instructing us to remain in our seats. A few minutes later, it was announced that we were to have an early intermission while they prepared to resume the performance.
We were not told what was wrong, but on my way to the lobby, I heard several people saying that singer playing Marthe had fallen. I checked Twitter and got the same information. When we returned to our seats, an announcement was made that Wendy White (playing Marthe) had fallen “a short distance” and had been “taken to the hospital as a precautionary measure”, but that she had not been hurt seriously. (A short distance? If you call falling off my second floor deck a short distance, then that’s about what it was.)
After intermission, it was announced that Teddy Hanslowe would continue as Marthe (which she did admirably), and the opera went on. (Jonas Kaufmann remained gorgeous throughout.)
Best wishes to Wendy White for a speedy recovery!