A second customer died from an allergic reaction to a product bought from Pret a Manger, the chain has confirmed.
The individual died in 2017 after eating a “super-veg rainbow flatbread” which was supposed to be dairy-free.
The company said it was mis-sold a guaranteed dairy-free yoghurt, which contained dairy protein.
The case follows the inquest into the death of Natasha Ednan-Laperouse, 15, who went into cardiac arrest after eating a Pret baguette in 2016.
The second customer died on December 27 last year after buying the sandwich from a store in Stall Street, Bath.
Pret said the yoghurt in the product was supplied by Coyo, a coconut milk brand which is stocked in shops and supermarkets across the UK.
The chain said it withdrew all affected products as soon as it was made aware of the incident by Bath and North East Somerset Council.
A spokesman said subsequent testing by Pret and two independent authorities found the Coyo dairy-free yoghurt contained traces of dairy protein.
Pret then ended its relationship with Coyo and is in the process of taking legal action, he added.
Coyo recalled all of its dairy-free coconut yoghurts in February after they were found to contain dairy.
The vegan brand was investigated by the Food Standards Agency, along with Bexley council in London, where Coyo is based, before it issued an allergy alert.
A spokesman for Pret said: “Our deepest sympathies are with the family and friends of our customer in this terrible case and we will seek to assist them in any way we can.”
Coyo previously said it was “devastated” to discover dairy in its yogurts, “especially as being dairy-free sits at the heart of everything we do”.
In a statement issued in February the company said it had carried out a “thorough review” of its ingredients and identified that the contaminated material was provided by an external third-party supplier, whose relationship had now been terminated.
On Wednesday Pret announced it would list all ingredients on its freshly made products following the death of Ms Ednan-Laperouse.
The teenager, from Fulham, south-west London, suffered a fatal allergic reaction on a flight after eating a sandwich from a Pret store at Heathrow Airport in 2016.