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Canadian pipeline operator TransCanada has announced that the southern leg of its Keystone XL, running from Oklahoma to the Texas Gulf Coast, is already operational.

Company spokesman Shawn Howard told the Houston Chronicle in an email that TransCanada started injecting oil into the pipeline at about 10:04am Central Time on Dec. 7, thus moving closer to the official launch of commercial services.

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Completion of the southern leg of Keystone cost TransCanada $2.3 million. The pipeline section is expected to be operating at full capacity by the end of the year and will move about 3 million barrels of oil. The daily capacity of the line is 700,000 barrels of oil per day, the newspaper said.

While the launch of the southern leg of the pipeline is undoubtedly a milestone for the company, the construction of its northern leg leading from Alberta's oil sands to Nebraska remains shrouded in doubt. As President Obama is yet to announce his decision on the trans-border project, protests from environmental groups continue to add pressure. They claim that constructing the pipeline would lead to a boom in development of Canada's oil sands, which in turn would cause a significant increase in greenhouse gas emissions and prevent the United States from meeting its carbon reduction targets, the Houston Chronicle noted.