ATLANTA -- Fuel supplies in at least five states are threatened by a gasoline pipeline spill in Alabama, and the U.S. Department of Transportation has ordered the company responsible to take corrective action before the fuel starts flowing again.

Colonial Pipeline Co. must conduct testing and analysis on the failed section of the pipeline, according to the department's Pipeline and Hazardous Materials Safety Agency, which is investigating the spill in rural Alabama.

The company has acknowledged that between 252,000 gallons and 336,000 gallons of gasoline leaked from a pipeline near Helena, Alabama, since the spill was first detected Sept. 9. It's unclear when the spill actually started. The pipeline section that failed runs from Mississippi to Atlanta.

The agency said the spill is "within an unusually sensitive ecological area" and it ordered Colonial to take action "to protect the public, property and the environment from potential hazards."

"The department will remain on site to carry out its investigation, and make sure the operator is taking the necessary steps to prevent any future incidents," agency administrator Marie Therese Dominguez said in a statement.

In a statement Saturday, the Alpharetta, Georgia-based company said that repair work had begun in an effort to return the pipeline to service "as rapidly and safely as possible."

The company said it is shipping as much gasoline as possible on its distillate mainline, or Line 2, in order to mitigate the impact of the pipeline that has been shut down. Colonial earlier said most of the leaked gasoline is contained in a retention pond near the city of Helena and there's no public safety concern.

In response to the shutdown, the governors in Alabama, Georgia and Tennessee announced they would lift restrictions on the number of hours that truck drivers delivering fuel can work, in hopes of preventing fuel shortages. Governors can suspend federal transportation regulations during emergencies.

A spokeswoman for Alabama Gov. Robert Bentley said Friday that he's in communication with pipeline company officials along with state and federal officials assisting at the spill location.

Georgia Gov. Nathan Deal said he was confident his order lifting restrictions for drivers would help.

"We are confident these measures will help ensure Georgians' uninterrupted access to motor fuel until Alabama's pipeline is fixed," Deal said in a statement.

Tennessee Gov. Bill Haslam said his order was a precautionary measure.

"We are not currently seeing any widespread unavailability of petroleum in Tennessee," Haslam said in a statement. "We urge Tennesseans to maintain their normal fuel purchasing and driving patterns to help prevent any potential impacts on our fuel supply while the pipeline undergoes repairs."

The U.S. Environmental Protection Agency waived requirements this week that metro areas with air quality issues in Georgia and Tennessee use a cleaner-burning type of gasoline during the summer months. That requirement of the Clean Air Act expired at midnight Thursday.