Cleanup continued Friday at the site of an oil pipeline leak and spill beyond an old farmstead on the Steve Jensen farm. Kevin Cederstrom/AP

When a North Dakota pipeline ruptured and sent over 20,000 barrels of crude oil gushing across a wheat field, it took officials nearly two weeks to inform the public about it.

The spill -- the biggest in the state since it became a major producer -- comes at a time when concerns are growing over the safety of the U.S. pipeline network, which is pumping more oil than ever to bring shale oil and Canadian crude to U.S. refineries.

State officials said they believed the spill to be much smaller than it actually was and said that was one of the reasons no public announcement was made for 11 days – and then only after The Associated Press asked about it.

Critics, however, said this is typical of the state.

“It shows an attitude of our current state government and what they think of the public,” said Don Morrison, executive director of the Dakota Resource Council, an environmental-minded landowner group. “It’s definitely worrisome. There is a pattern in current state government not to involve the public.”

The leak, an estimated 20,600 barrels, was discovered by farmer Steven Jensen on September 29 while harvesting wheat on his farm about nine miles northeast of Tioga, North Dakota. The North Dakota Health Department was informed of the spill the same day.

“It was pretty ugly,” Jensen said. The nearby crop had “disintegrated, you wouldn’t have known it was a wheat plant.”

Workers were continuing with the cleanup in Jensen's field Friday. Three excavators were scooping up contaminated soil and dumping it into yellow shipping containers late Thursday. Security personnel kept on-lookers at bay while men in hard hats worked on the site.

Jensen said his wheat field resembled “an excavation war zone” and said his land is ruined for farming for the next few years.

The pipeline is owned by San Antonio, Texas-based Tesoro, which said the cleanup costs are estimated at about $4 million and could take anywhere from a couple of months to a couple of years.

Kris Roberts, an environmental geologist with the North Dakota Health Department, said that while companies must notify the state of any spills, the state doesn’t have to release that information to the public.

That’s not unusual in major oil-producing states: Alaska, Oklahoma and Texas also do not require the government to publicly report spills. North Dakota is the number two oil producer after Texas.

While authorities say no lakes, streams or rivers were within five miles of the spill, the incident could provide ammunition to environmentalists who argue water supplies are endangered by construction of the proposed Keystone XL pipeline from Canada to Oklahoma.

Though authorities said no water sources were contaminated, no wildlife was hurt, and no one was injured, local environmentalists remain skeptical.

“When seven acres of agricultural land is affected and they say there was no environmental impact, it defies common sense and logic,” Morrison said.

“Obviously, if you have an oil spill, some species of wildlife are going to be impacted, no matter where you have a spill,” said Wayde Schafer, a North Dakota spokesman for the Sierra Club.

Roberts said his agency’s response was appropriate. He said Tesoro reported the spill to state regulators within one day after Jensen found it. A state regulator was on site within hours.

“We deal with a spill and make sure it’s cleaned up … we don’t issue press releases,” Roberts said.

Some other state officials are concerned about how they found out about the spill.

“There is almost a million gallons of product on the ground and we need to find out what happened,” said Brian Kalk, chairman of the North Dakota Public Service Commission. “I’m upset that we didn’t find out until yesterday.”

Kalk said the three-member commission routinely gets updates on even the smallest spills, but he wasn’t notified of the Tioga spill until Thursday. One of the commission’s jobs is to regulate where pipelines are placed.

The ruptured pipeline is part of Tesoro’s “High Plains” pipeline system in North Dakota and Montana, which gathers oil from the Bakken shale field – which straddles the U.S.-Canada border – and delivers it to another pipeline and Tesoro’s 68,000 barrels per day Mandan refinery.

New developments in hydraulic fracturing, or fracking, have caused a boom in North Dakota’s oil production. Oil output jumped from 125,000 barrels per day in 2007 to 875,000 bpd in July, 2013.

Al Jazeera and wire services