TransCanada's permit to operate its Keystone tar sands pipeline in South Dakota could be revoked if an investigation into last week's 210,000-gallon leak determines that the pipeline operator violated its license, Reuters reported.

State regulators expressed concern that the Nov. 16 spill in Marshall County was not the first from the controversial pipeline.

"This is a relatively new pipeline. It is supposed to have an operating life of more than 100 years and it was supposed to be a state-of-the-art pipeline construction. It appears that it is not," South Dakota Public Utilities Commission (PUC) member Gary Hanson told Aberdeen News.

"We've had three fairly major leaks just on the border with North Dakota and two in South Dakota in a very short period of time," Hanson added. "One might expect this to take place on a pipeline over a period of 30 or 40 years at the maximum, yet it's been fewer than 10 years."

In April 2016, the Keystone pipeline gushed 16,800 gallons of oil near Freeman, South Dakota.

According to Reuters, the permit that the PUC issued for the Keystone in 2007 had 57 conditions that include construction standards and environmental requirements. The PUC can revoke or suspend the permit if TransCanada is found to have made misstatements in its application or does not comply with the conditions. The PUC is expecting a preliminary report about the spill from federal and state technical experts in the next 10 days.

“We are waiting to see what the forensic analysis comes back with to see if any of our conditions were violated," PUC chair Kristie Fiegen told the news service.

The other two commissioners on the panel agreed.

“The PUC needs to determine whether any of the permit conditions for this pipeline were violated. Those conditions were placed on the permit to ensure safe construction and operation of the pipeline," commissioner Chris Nelson said.

“If it was knowingly operating in a fashion not allowed under the permit or if construction was done in a fashion that was not acceptable, that should cause the closure of the pipe for at least a period of time until those challenges are rectified," added commissioner Hanson.

As for the status of last week's spill, TransCanada said on its website that 160 crew members are on the spill site removing oil. As of Nov. 21, more than 16,000 gallons of oil have been removed using hydro-vac and excavation equipment.

Company spokeswoman Jacquelynn Benson told the Associated Press that the cause of the leak is still unknown.