Five million litres of a bitumen-water-sand emulsion were found to have leaked Wednesday from a Nexen Energy pipeline south of Fort McMurray, Alta. — one of the biggest oil spills in the province's history.

It adds further fuel to the debate over pipeline safety that continues to rage on, most recently emerging as a point of contention among premiers meeting in St. John's this week.

It's not the first time crews have been dispatched to clean up a leak. 

Here are six other pipeline spills in Alberta:

Little Buffalo 

In April 2011, almost 4.5 million litres of crude oil leaked near the First Nations community of Little Buffalo in northwest Alberta — the largest spill in the province in 35 years.

The oil contaminated more than three hectares of beaver ponds and muskeg in a densely forested area northeast of Peace River, Alta. 

The Energy Resources Conservation Board, an independent government agency that was dissolved in 2013, reprimanded the company, saying it had inadequate leak detection and failed to test its emergency response plan.

Alberta's premier at the time, Ed Stelmach, also criticized the oil company's poor communication with the First Nation, as well as with the province itself, following the spill.

Plains Midstream, the company that owns the pipeline, was charged with three counts of violating environmental protection laws.

Red Deer River

Plains Midstream got into trouble again with another spill in June 2012, this time into a central Alberta river system.

Almost half a million litres of sour crude oil leaked into a creek that flows into the Red Deer River located about 100 kilometres north of Calgary near the community of Sundre.

Alberta Pipeline Spill 20120608

Oil from a Plains Midstream pipeline leak coats a pond near Sundre, Alta., in June 2012. It was the second major spill from a pipeline owned by the company in a just over a year. (Jeff McIntosh/Canadian Press)

 

The 461,000-litre spill (about 2,900 barrels) prompted further strong criticism from Alberta's energy watchdog. The regulator concluded Plains Midstream didn't inspect its pipeline often enough and didn't pay enough attention to government warnings. 

It also said the company failed to enact adequate mitigation measures once the leak occurred and communicated poorly with hundreds of people affected by the spill.

The company was charged with two counts of violating environmental laws in June 2014. 

It was ultimately fined $1.3 million after pleading guilty to the charges for both spills.

Elk Point

A pipeline flange gasket failed at an Enbridge pumping station northeast of Edmonton and spilled about 230,000 litres (1,400 barrels) of crude oil in June 2012

The spill was almost completely contained to the site near Elk Point, Alta., with no impact on wildlife or water, Enbridge said at the time.

It was the third major pipeline oil spill within a one-month time span in Alberta, after spills at Red Deer River and Rainbow Lake.

Slave Lake

An aboveground pipe failure owned by Canadian Natural Resources caused 70,000 litres of oil and processed water to spill near Slave Lake, Alta. 

The spill, which happened in April 2014 about 250 kilometres north of Edmonton, wasn't an emergency, according to the Alberta Energy Regulator. 

It didn't leak near any people, water or wildlife, the regulator said.

Red Earth Creek

Just a few months later, a Canadian Natural Resources-owned pipeline spilled oil again into muskeg in northern Alberta. 

About 60,000 litres of crude oil leaked in November 2014 when the pipeline experienced a mechanical failure. A report by the regulator said wildlife was not affected.

Low amounts of hydrogen sulphide gas were also detected along with the crude oil.