Seven people were treated in hospital following a chemical leak at a bakery in Leicester.
The leak happened at 8.30am on Wednesday at the Bradgate Bakery on Madeline Road, which was evacuated.
Emergency crews from Leicester Fire and Rescue Service responded to the incident with six fire engines and "a number of chemical support vehicles".
A spokesman said 23 casualties at the site were affected by gas inhalation, with 16 treated at the scene.
The East Midlands Ambulance Service said a further seven people were transported to the Leicester Royal Infirmary to be treated for gas inhalation.
There are no hazards to local residents, but the cause of the leak has not been discovered.
The spokesman said: "There was a chemical leak which caused chemicals to mix and create a gas, but we don’t know the substances or full cause yet. The small gas cloud caused by the leak has been safely dispersed, and there are no further chemical leaks."
Bradgate Bakery is part of a fourth generation family-owned business, Samworth Brothers, and employs 1,600 people.
A spokesman for Samworth Brothers said a full investigation into the chemical leak was under way and that five of the seven workers sent to hospital had now been discharged.
"We can confirm a chemical leak in the one area of the Bradgate Bakery site was identified this morning and the emergency services were called," the spokesman said. "As the fire brigade has outlined, the incident has now been contained.
"As previously reported seven people were taken to hospital for observation. Five of these individuals have subsequently been discharged. Two remain for observation. A full investigation is under way."