Corrections & Clarifications: A previous version of this story misstated the day McNally gave birth. She gave birth early Monday.

A tanker carrying about 4,000 gallons of jet fuel overturned and exploded near I-70 and I-465 on the city's east side, closing lanes and backing up traffic on both interstates.

Authorities began receiving calls reporting an overturned semi and fire on the ramp from I-465 southbound to I-70 eastbound just before 2 p.m., Indianapolis Fire Department Battalion Chief Rita Reith said.

Traffic cameras on the interstate showed a large fire that engulfed much of the ramp as fuel poured from the tanker. The fire caused "severe, catastrophic damage" to the surrounding area, Reith said, spreading nearly 500 feet and affecting both sides of the bridge.

The tank split open when the semi overturned, Reith said. The damage to the truck was devastating.

"If you can imagine a 4,000 gallon metal tank split open," she said, "there is just not much left of it."

The good Samaritans

The 59-year-old driver was able to get out of the truck on his own, Reith said, but was met by three good Samaritans who helped usher him to safety. The people who helped the driver were uninjured, said Indiana State Police Sgt. John Perrine.

"Without question, those good Samaritans saved this driver's life," he said.

One of the good Samaritans, Holly McNally, gave birth to her fourth child early Monday morning. She and her mother were driving home from the hospital, where he remains in the neonatal intensive care unit, when she saw a man on fire.

She ran to him.

As she was running, she encountered another man who had a blanket they used to extinguish the flames and cover the driver. When they got to the driver, McNally could see he was severely burned.

Read more of Holly McNally's story: A good Samaritan and a new mother

Then came the first explosion.

“We started to go down the embankment a little bit, and I could smell the fluid running past my feet,” she said. She asked the man what he’d been hauling: jet fuel. “I was like, ‘You guys, we have got to get out of here.’”

A second explosion caused the fire to spread, following them down the embankment. The driver, who appeared to be in shock, began to slow down. Thankfully, another man showed up to help usher them to safety.

The driver was taken to an area hospital in critical condition, Reith said. Perrine said he suffered "significant burns."

No other vehicles were involved in the incident, Perrine said.

"Any time you have an incident this large or a fire this large," he said, "I think we're very fortunate that it didn't involve more than just the one vehicle."

The incident remains under investigation, although investigators believe the driver may have taken the exit at an unsafe speed, contributing to the roll-over.

Firefighters on scene were able to get the fire under control within 40 minutes, Reith said. The bridge will need to be inspected for any signs of significant structural damage.

In a brief Periscope live video from the bridge, Indiana Department of Transportation engineer Brian Harvey said the intense heat from the fire caused the moisture inside the bridge's concrete barrier to boil. The boiling caused small chunks of the concrete to explode from the barrier, dotting the roadway.

What we know:About the jet fuel tanker fiery explosion

Traffic was jammed for hours on both interstates well into the evening.

INDOT tweeted that the debris had been cleared, sandblasted and the highway was reopened by about 2:30 a.m. Friday.

Call IndyStar reporter Holly Hays at 317-444-6156. Follow her on Twitter: @hollyvhays.

Call IndyStar reporter Amelia Pak-Harvey at 317-444-6175 or email her at apakharvey@indystar.com. Follow her on Twitter @AmeliaPakHarvey.