Millions of liters of crude oil gushed out of a breached pipeline in southern Israel early Thursday, causing what one Environmental Protection Ministry official called "one of the gravest pollution events in the country's history."

The official, Guy Samet, said there is a seven-kilometer (4.3 mile) long river of oil flowing through the Evrona Nature Reserve in southern Israel, some 20 kilometers (about 12 miles) north of Eilat.

Firefighters, police, Environmental Protection Ministry officials and oil pipeline maintenance teams were dispatched to the site of the spill, and managed to curtail the flow after about two hours.

The breach occurred during maintenance work that was part of preparations for the international airport under construction in Timna, in southern Israel. Once the leak was discovered, pipeline company officials shut the pipeline's valves – but not in time to prevent the spillage of millions of liters of oil.

The pipeline, which links Eilat to the port city of Ashkelon, opened in the 1960s to facilitate the movement of Iranian oil from the Persian Gulf to European markets. Since the rupture in Israeli-Iranian relations in 1979, it has mostly been used to move oil and oil products from Eilat to different parts of Israel.

The Environmental Protection Ministry's Green Police is investigating the cause of the spill, whether it could have been prevented and how it was handled once discovered.

Eilat Police ruled out foul play as the cause of pipeline breach, saying it was likely caused by a technical malfunction from previous maintenance work.

The main road leading to Eilat, a Red Sea resort, from central Israel was closed intermittently as emergency teams contained the leak.

Evrona Nature Reserve, one of the most important reserves in the Arava, is home to a large deer population and the northernmost douma palm trees in the world.

"Crude oil flowed throughout the reserve, causing serious damage ... to flora and fauna," Samet told Israel Radio on Thursday. He estimated the spillage at millions of liters.

"Rehabilitation will take months, if not years .. This is one of the State of Israel's gravest pollution events. We are still having trouble gauging the full extent of the contamination."

There was no damage on the Jordanian side of the frontier. However, Jordanian news outlets reported that large amounts of hydrogen sulfide were detected in the air around Aqaba – and some reports said that more than 80 people were hospitalized with breathing difficulties after inhaling fumes.

Shaul Goldstein, director-general of the Nature and Parks Authority, said the authority would examine the conduct of the oil pipeline company to determine whether the spill was an accident or a result of negligence.

"We must examine whether the company fulfilled the detailed guidelines about this type of oil pipeline work that were formulated with the Environmental Protection Ministry after the serious pollution cause by the leak at Nahal Zin," he said, referring to a previous ecological disaster.

Doron Nissim, director of the nature reserves and national parks in Eilat, said hundreds of acres of nature reserve were damaged by the spill. The main threat is to insects and rodents that live on or close to the surface, Nissim said, adding that the pollution has not seeped deep into the ground. He also said the nature reserve's deer population is not at risk.

Treating the pollution caused by the spill will require removing large swaths of land that are steeped in oil, which will further damage the surface, said Dr. Gilad Golub, CEO of the Environmental Services Company, a state-owned firm that deals with all the hazardous waste produced in Israel.

Several hours after the spill occurred, oil pipeline company tankers began pumping oil wherever possible. "It is important to extract as much oil as possible," said Golub, "but the most heavily polluted land must be removed immediately afterward. This land must be burned."

Golub said that less polluted land should be removed as well and treated using bacteria that break down the pollutants. If that doesn’t happen, the oil will seep further down into the land and rainfall will cause it to spread and contaminate other parts of the reserve.

The Evrona reserve covers some 17,000 dunams (4,200 acres) of land.

This is not the first time an Israeli nature reserve has been damaged by oil pipeline maintenance. In June 2011, the reserve at Nahal Zin in the Negev was damaged when 1.5 million liters of jet fuel leaked into the soil.

Bilha Givon, director of the nonprofit Sustainable Development for the Negev, said, “It is amazing that in 2014 there is no technology to identify a leak so that it is possible to stop it, especially when this is not the first time.”

The Zalul environmental nonprofit added, “The Eilat Ashkelon Pipeline Company must be opened to public supervision. It would be appropriate in this case to also raise questions about the preparedness to prevent failures in offshore oil and gas drilling.”

MK Dov Khenin (Hadash), the chairman of the Social-Environmental Lobby in the Knesset and sponsor of an amendment to the Oil Law, said, “This disaster was expected. That's how it is when the government insists on managing the oil issue based on an out-of-date law from 1952, which was written before they thought about environmental problems. Regulating the oil industry, including its transport, requires modern and professional legislation.”