NEWBURYPORT — Local and environmental officials responding to a gasoline spill that found its way to the Merrimack River yesterday urge people to stay out of the water until they are notified the gas has evaporated.

Because the spill came dangerously close to the city's water supply, public service officials took precautionary measures and assured residents their tap water is safe.

In spite of efforts by the Coast Guard, the state Department of Environmental Protection and hazardous material cleanup teams to contain yesterday's fuel spill on Interstate 95, the Environmental Protection Agency says between 8,000 and 9,000 gallons of fuel drained into the surrounding area.

The 10,000-gallon tanker nearly collided with a car that flipped into northbound traffic from a southbound lane. The tanker jackknifed and landed on its side about 9:15 a.m. The accident occurred less than a mile from the Whittier Bridge and close to the Spring Lane pumping station, the city's water treatment facility.

As cleanup crews attempted to halt the gasoline's progress to the Merrimack River, a "significant" amount of the tanker's fuel found its way into the river estuary by way of a storm drain.

As of yesterday evening, city, state and federal officials were striving to minimize soil and water contamination in the area. Officials were concerned throughout the day about explosive fumes settling in the Laurel Road neighborhood and about gasoline spreading throughout the river grasslands.

The federal Environmental Protection Agency immediately deployed two on-scene coordinators and cleanup contractors immediately. Assisting throughout the day were the Coast Guard, DEP, Enpro Environmental Services and local harbor patrol units, who worked to secure a 500-foot perimeter in the river to keep boats away from the fuel floating on the surface.

Officials managed to contain most of the spilled gasoline in the Merrimack through the use of two 750-foot containment booms.

The risk in allowing gasoline to spread is its potential to damage wildlife as it comes into contact with the gasoline at the surface, Newburyport Harbormaster Ralph Steele said. Steele's harbor patrol unit aided DEP officials in deploying the first boom containment system and maintaining a 500-foot perimeter around the site to keep boat traffic away from the spill. "We've had a boat there all morning," said Steele, who said the accident could have been far worse if the tanker had been carrying oil.

"Gasoline evaporates very rapidly, so it's not anywhere as environmentally damaging as oil," Steele said. "If you can contain it, it should evaporate pretty quickly."

While gasoline has the potential to kill fish and living organisms in the ecosystem, Newburyport Conservation Commission Agent Mary O'Brien said she's not been apprised of what damage might have occurred as a result of the spill.

"It's not good," O'Brien said of the effect gasoline could have on the river and aquatic habitat. "I'm no expert on how the gas would affect fish and wildlife, but I suspect it would kill anything depending on the amount and how concentrated it is in certain areas."

According to an EPA press release, Mass DEP is continuing to deploy boats and boom material to the river where they are working to contain the gasoline. In addition, a Field Assessment and Support Team vehicle, known as a FAST vehicle, is monitoring air conditions and assessment activities.

The Massachusetts Division of Marine Fisheries is planning to conduct an assessment on potential impacts to shellfish resources.

Local officials concerned about Newburyport's water supply have shut down a private well and sewage lift station near the site. The crash site is about 1,000 feet from two of the city's wells, and about 1,300 feet from the city's water treatment facility, but officials say the water supply is safe.

"It's unlikely any public water supply is impacted, but the nearest wells were shut down as a precaution," said Mass DEP spokesman Joe Ferson. "Those water supplies have adequate storage to continue operating."

Salisbury Harbormaster Ray Pike has been telling boaters in the area to stay out of the water, even though he believes the gasoline will likely evaporate or drift out to sea with the next two outgoing tides.

"It is a lot of gas," he said. "It's a whole lot of gas, but gas evaporates, so it will be gone."

The EPA is also deploying additional cleanup contractors to assist with containment of fuel on the river and eventual cleanup of the Merrimack River and impacted coastal areas.