UPDATED 1.19PM: Two men were taken to Tauranga Hospital after an incident involving chemicals at Ballance's superphosphate manufacturing plant at Mount Maunganui.

The men are believed to have been working with the poisonous, colourless gas, Hydrogen Sulphide, at Ballance Agri-Nutrients on Hewletts Road when they accidently inhaled fumes about 4.53pm, say emergency services.

Two men were taken to Tauranga Hospital as a precaution after inhaling hydrogen sulphide.

Mount Maunganui St John Paramedic shift manager Gary Bishell says ambulance staff were called to the scene to treat the two patients.

'A 40-year-old Te Puke man and a 57-year-old Tauranga man were both taken to Tauranga Hospital as a precaution.”

Both men have since been discharged from hospital, says a Bay of Plenty District Health Board communications spokesperson.

Mount Maunganui, Tauranga and Greerton Fire Brigades were also called to the incident.

Northern Fire Communications shift manager Megan Ruru says ambulance staff requested assistance from firefighters but the brigades were not required to do anything when they arrived at the scene.

Ballance Agri-Nutrients general manager of fertiliser operations and distribution Greg Delaney says emergency services were called to Ballance's superphosphate manufacturing plant at Mount Maunganui late yesterday afternoon."

Greg says emergency services werecalled because one person collapsed and two men, who were inside the laboratory at the time of the incident, were taken to hospital as a precaution.

"As the incident occurred in the laboratory, with the potential for exposure to chemicals and gases, Hazmat and the fire brigade were alerted by emergency services. Investigations and atmosphere testing confirmed the area was safe.

"At this stage the cause of the collapse is unknown."

Hydrogen sulphide is the chemical compound with the formula H2S. It is a colourless gas with the characteristic smell of rotten eggs. It is heavier than air, poisonous, corrosive, flammable and explosive.

Swedish chemist Carl Wilhelm Scheele is credited with having discovered hydrogen sulfide in 1777.