In which air attack in 1943 during the Second World War was mustard gas released?

"On Dec. 2, 1943, a German air attack sank 17 merchant ships in the Italian port of Bari. One of the ships destroyed that day was carrying a secret cargo of 100 tons of mustard gas bombs. The bombs exploded, releasing sulfur mustard into the harbor and the air. Many soldiers and civilians were injured or died from the mustard gas effects."

https://www.cdc.gov/nceh/stories/mustard_gas.html

Sulfur Mustard was used at the air raid on Bari Harbour, Italy on December 2nd 1943.

The only combat casualties from sulfur mustard in WWII were those injured or killed following a German air raid on the harbor of Bari, Italy, on December 2, 1943.

https://www.ncbi.nlm.nih.gov/books/NBK236059/#:~:text=The%20Bari%20Harbor%20Disaster,Perera%20and%20Thomas%2C%201986).