Two people are being flown to Wellington Hospital in a critical condition after being exposed to hydrogen sulfide in a chemical spill at a tanning factory in Wanganui.
Another 19 people have been exposed to the gas, and were being assessed at Wanganui Hospital, a DHB spokeswoman said.
Emergency services were called to Tasman Tanning in Castlecliff about 5pm today following a chemical spill.
The spokeswoman said two people had been ventilated after being exposed to the toxic gas.
They were in a critical but stable condition and were due to fly to Wellington Hospital for further treatment tonight.