The Department of Labour is investigating a chemical spill in Whanganui which has left two people in a critical condition.
Twenty-one people, including a fire-fighter and five ambulance staff, were treated at Whanganui Hospital after inhaling the highly toxic gas Hydrogen Sulphide.
Two men had to be airlifted to Wellington Hospital last night, while the others have since been discharged.
Emergency services had rushed to the Tasman Tanning leather treatment plant in Castlecliff just before 5pm yesterday when the tanning process went wrong.
Hydrogen Sulphide, a colourless, poisonous and flammable gas can damage lungs and affect breathing.
RadioLIVE