Officials closed all northbound lanes of Interstate 95 near Dumfries for three hours yesterday morning after a flatbed truck carrying barrels of insecticide overturned and spilled more than 100 gallons of the liquid across the highway.

Virginia State Police spokeswoman Lucy Caldwell said the truck overturned after it blew a tire about 9:15 a.m. at mile marker 151, between Triangle and Dumfries in southern Prince William County. The truck flipped over and blocked all three lanes of traffic, spilling insecticide from one of two barrels strapped to its flatbed.

"The liquid splashed out of the barrel and across the road in a wide slick," Caldwell said. "It appears that no one traveled through it, and all the traffic was able to stop without incident." Officials closed the highway at 9:30 a.m. when fire and rescue crews arrived. Northbound traffic was backed up as much as eight miles to Aquia in Stafford County. State police rerouted traffic onto Route 1 in Stafford County and allowed cars to reenter the interstate just north of the crash, at Route 234. Two lanes of I-95 were reopened at 12:20 p.m.

The truck, owned by Potomac Waterproofing, was heading north after completing a job in Stafford County when a tire blew and the rig flipped. The truck was carrying several hundred gallons of the commercial pesticide Prevail, which is used primarily to kill termites.

Caldwell said officials were initially concerned that the pesticide, which is toxic to fish, had seeped downhill into nearby Quantico Creek, a Potomac River tributary. Inspectors from the Department of Environmental Quality and the Department of Emergency Services later determined that the spill was contained to the highway and surrounding shoulder and did not make its way to the water below.

The truck's driver, Neptali Mejia, 34, of Manassas Park, has not been charged in the accident, which did not include any other vehicles.

Yesterday's insecticide spill was the summer's second major truck crash involving hazardous materials on northbound I-95 in the Washington area. This cleanup effort paled in comparison to the shutdown of large portions of the Springfield interchange on June 2, when both rush-hour commutes came to a standstill as officials worked to clear an overturned truck carrying explosive black powder.

The June 2 incident lasted more than 16 hours as Fairfax County and state officials decided how best to open the truck, which they feared could explode with even small amounts of friction or static electricity. The region's network of roadways was crippled for most of that day as emergency crews from across the northeast evaluated the truck, which was overturned on the ramp connecting I-95 northbound to the Capital Beltway.

CAPTION: The truck owned by Potomac Waterproofing flipped over after a tire exploded, and the pesticide Prevail spilled onto the northbound lanes of Interstate 95.