The municipal government for the Fort McMurray region is facing environmental charges for an incident two years ago in which chlorine gas was released inside the community's water treatment plant.

The Alberta government has charged the Regional Municipality of Wood Buffalo (RMWB) with four counts under the Environmental Protection and Enhancement Act and one charge related to the transportation of dangerous goods.

The environmental charges relate to the release of a substance into a waterworks system that could cause an adverse effect.

The offences are alleged to have occurred between May 8 and May 17, 2017.

Provincial spokesperson Jess Sinclair told CBC News the investigation stems from a May 8 incident at the Fort McMurray Water Treatment Plant.

A driver allegedly dumped 5,400 litres of bleach inside a polyaluminum chloride bulk tank at the water treatment plant which sits on the northern bank of the Athabasca River overlooking downtown Fort McMurray.

The bleach caused a chemical reaction and a toxic chlorine gas was released into the air, Sinclair said.

A statement from the RMWB at the time said the chlorine was accidentally transferred into the bulk tank during a routine chemical delivery.

Operations staff immediately shut down the water treatment plant following the incident.

Alberta Health Services was contacted regarding the incident but there were no concerns about water quality, the municipality said in a news release a few hours following the incident.

An employee was treated as a precaution for inhalation concerns but was not injured.

The municipality's first court appearance is set for Wednesday in Fort McMurray.