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A semitrailer carrying a hazardous chemical — the same one that was a catalyst in massive explosions elsewhere in the U.S. — tipped over on Interstate 15, closing the freeway for nearly eight hours Wednesday.

The incident on the major traffic artery started about 9:15 a.m. when the truck tipped in the northbound lanes near 6100 South in Murray after a multivehicle crash. Both directions of the freeway were closed for most of the day, leading to snarled traffic throughout the valley's surface roads.

Though no one was injured, said Utah Department of Public Safety (DPS) spokeswoman Marissa Villasenor, the incident could have been catastrophic because of what the tanker was carrying. There was no leakage of the haul's material — ammonium nitrate — but authorities feared that the substance could have potentially leaked out.

While not explosive on its own, ammonium nitrate can be combustible if mixed with other substances.

The substance, often found in fertilizers, ignited after a fire at a Texas plant in April 2013. The chemical caused a massive explosion there that killed 15 people. Hundreds of others were injured, and parts of the town of West were left in shambles.

The blast also created a 2.1-magnitude earthquake.

Villasenor was unsure how much the tanker on I-15 held, but a large amount mixed with other chemicals could have caused a large explosion in the area, possibly damaging the freeway and perhaps extending beyond.

The DPS sent a hazardous-materials team to handle the cleanup, and Utah Highway Patrol expanded the area of road closures around the scene from a 150-foot radius to a half-mile radius.

As a result, I-15 traffic was closed northbound at 9000 South, while southbound traffic was being diverted onto westbound I-215. UHP also temporarily closed I-215 at Union Park and eastbound I-215 at Redwood Road until the work was done.

Southbound lanes reopened about 3 p.m., and northbound lanes opened just before 5 p.m.

Early on, the accident had northbound motorists backed up as far as 11200 South, while bumper-to-bumper southbound traffic was reported through the valley south of 4500 South. At one point, South Jordan police were called upon to deliver a baby in a car — both mother and child were fine afterward.

The restrictions also caused delays on FrontRunner and TRAX, through the general area of the incident.

The cause of the crash was under investigation Wednesday evening, but troopers initially reported that a small black trailer appeared to have come loose from a pickup truck, triggering a chain reaction.

remims@sltrib.com, mnoble@sltrib.com, ctanner@sltrib.com Twitter: @remims, @mnoblennews, @courtneyltanner