PHOENIX — Interstate 10 in Tucson reopened in both directions Wednesday evening after a fatal crash involving a toxic spill shut down the freeway for more than a day.

A shelter-in-place order was lifted around 5 p.m. for the area where a wreck caused a nitric acid spill on the I-10 a day earlier, while existing evacuations remain in effect.

Those within a 1-mile hazard zone in the southeast part of the city were told to stay indoors around 1:35 p.m., according to an Arizona Department of Public Safety update. About five hours earlier, people within 3 miles of the incident were told to stay inside because of the health risk.

I-10 has been closed in both directions between Kolb and Rita roads since a truck tractor pulling a box trailer crashed around 3 p.m. Tuesday and leaked nitric acid. The driver of the vehicle was killed, DPS said.

Those within half a mile of the incident were evacuated Tuesday by DPS and Tucson fire and police departments.

The University of Arizona Tech Park was among the facilities evacuated. Some schoolchildren in Rita Ranch were among those who sheltered in place, the Arizona Daily Star reported. Officials canceled classes at several nearby schools on Wednesday.

A shelter-in-place order was issued for a 1-mile perimeter after the wreck and lifted at 8:45 p.m. Tuesday. But DPS said gassing occurred when crews were working to remove the vehicle’s load, so the order was reinstated, initially at 1 mile, before 5 a.m. Wednesday.

People within the shelter-in-place perimeter had been advised to refrain from using heaters and/or air conditioners.

Nitric acid is used to make ammonium nitrate for fertilizers and in the manufacture of plastics and dyes.

Pima County’s health department and poison control center on Wednesday recommended that anyone who may have been in contact with the gas for more than 15 minutes get a medical evaluation if they develop respiratory difficulties like wheezing or shortness of breath. They said symptoms could be delayed up to 24 hours after exposure.

Health officials said it is possible that some people living within a mile of the accident may have been exposed to the material for more than 15 minutes if the building where they were sheltering in place was using an air conditioner or heater pulling in air from the outside. But they said that people who simply drove through or past the accident and chemical plume should not have been affected.

The Centers for Disease Control and Prevention’s website says nitric acid is a highly corrosive, colorless liquid with yellow or red fumes and can cause an acrid smell.

It says exposure to nitric acid can irritate the eyes, skin and mucous membranes. Depending on the dosage, it also can cause delayed pulmonary edema, pneumonitis, bronchitis and dental erosion.

The Associated Press contributed to this report.

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