A second man has died and another is still in a critical condition after a mystery toxic gas leak at a paper mill near Albury, on the border of Victoria.

The leak at Norske Skog site in Ettamogah at about 1.30pm yesterday prompted the evacuation of 150 workers, about a dozen of whom were taken to hospital.

A 28-year-old Wodonga man died yesterday afternoon.

A 37-year-old lavington man has died overnight.

A third worker, a 22-year-old Victorian man, remains in a critical condition.

A report will be prepared for the Coroner.

Photo: Nine News