“There has never been anything like this in our 32-year tournament history. We deeply regret the incident,” tournament director Ralf Weber said in a statement.
The woman didn’t suffer any “major injuries,” the statement added, but was taken to the hospital “for safety reasons.”
Weber also offered the spectator a season ticket for next year.
Event managers Dr. Udo Kleine and Uwe Greipel-Dominik said in a joint statement that they suspect “drumming against the boards caused screws to come loose.”
“This must not happen, and we apologise. We will also check all the other boards and their fixings immediately after the Zverev match,” they added.
Zverev, who is still searching for his first career grass title after defeat to Taylor Fritz in Sunday’s Stuttgart Open final, will play Italy’s Lorenzo Sonego in the second round.
The German has twice previously reached the final in Halle, in 2016 and 2017, and is aiming for his seventh career title on home soil.