Operators of the facility say the incident "had no impact whatsoever outside the plant"
An uncontrolled release has occurred at Poolbeg incinerator in Dublin.
11 men have been treated in hospital following the incident late last night.
First aid was administered at the scene and the men attended St Vincent's Hospital. Two are being kept under observation.
A spokesperson for Dublin Waste-to-Energy Ltd said: "Late on Wednesday night a small amount of lime was inadvertently released inside the flue gas treatment area during the commissioning and testing of the Dublin Waste to Energy plant at Ringsend.
"Combustion Unit No 1, which was operating at the time, was shut down in an orderly and controlled manner. The lime was contained within the building and did not escape into the environment and the incident had no impact whatsoever outside the plant."
The statement adds: "We are investigating to understand what exactly occurred, but it appears from preliminary investigation that the release of the lime was due to a problem with a door seal in the fabric filter baghouse."
Parent company Covanta says they will "investigate the incident thoroughly", while John Daly - the company's general manager here - insisted that the plant is safe.
The HSA says it is treating it as a dangerous occurrence, while the Environmental Protection Agency (EPA) also confirmed an incident occurred at the incinerator.
All quiet outside Poolbeg Incinerator after incident which saw 11 people hospitalised pic.twitter.com/FuFDgvpWSj— Sean Defoe (@SeanDefoe) June 8, 2017
A number of local politicians have raised concerns after the incident.
Green Party leader Eamon Ryan said: “We are extremely concerned at this incident happening so soon after incineration began at the site. The authorities need to get to the bottom of this as soon as possible. We’re calling for all activities at the site to cease while the investigation is carried out.”
Fianna Fáil Dublin City Councillor Paul McAuliffe called for the council to hold an emergency information meeting on the matter.
In a statement, he said: “The incinerator was lit for the first time last Wednesday and the first day of operation was Friday. It is deeply concerning that less than 7 days later a dangerous health and safety incident has occurred.
“The Government, together with the Dublin City Council officials responsible for oversight of the Poolbeg site must do what is necessary to assure the public that an incident of this nature will not reoccur."
Sinn Féin's Chris Andrews called for all work to cease at the incinerator, and said he would be bringing emergency motion to next Monday's DCC meeting over the matter.
"We will be demanding action and answers," he added.