Shares of Zensho Holdings, which operates Japanese restaurant chain Sukiya, fell as much as 7.1%, the most since Feb. 13, after the firm said a customer had found a dead rodent in its miso soup.

Sukiya said the animal made its way into the soup while meals were being prepared at a branch in Tottori Prefecture on Jan. 21, and that staff ¡°failed to notice¡± it before serving. The chain said in an announcement on Saturday that it would double down on hygiene measures.

The restaurant also apologized for failing to disclose the incident sooner. ¡°Many customers ended up feeling anxious and worried¡± as a result, it said.

Sukiya operates around 2,000 branches across Japan and is known for its beef rice bowls.

The long-term impact on Zensho¡¯s shares will depend on whether the rodent incident leads to a significant fall in customers, said Shoichi Arisawa, an analyst at Iwai Cosmo Securities.

Zensho¡¯s stock had been rising due to hopes of a profit boost from recent price hikes, Arisawa said. The shares have gained around 25% in the last 12 months, outperforming the Topix index.

¡°I don¡¯t think the incident reflects a structural problem with the business. But Sukiya can¡¯t just dismiss it as a one-off accident,¡± Arisawa said.