LEBANON COUNTY, Pa. (WHTM) — A massive backup on Interstate 81 South Wednesday afternoon involved 20 to 25 tractor-trailers in more than a dozen crashes.

One person died.

10 miles of I-81 were shut down for hours. In total, state police say there were 14 crashes, including three hazmat incidents.

The first crash happened at about 2 p.m. on I-81 south near mile marker 87.

State police say one truck tried to pass another, but the two trailers collided. There was heavy rain at the time.

Less than 10 minutes later, six vehicles were involved in a crash.

Police say for unknown reasons, a tractor-trailer driver didn’t notice traffic slowing or stopping and struck another vehicle at a high speed, which killed the driver.

Truckers were detoured to avoid the backup.

“We were delayed going through town because you had 20 or 30 tractor trailers that normally don’t be on the business street, on the business street,” said truck driver Steven Jenkins.

“33 miles which took me four hours,” said truck driver Moses Mubiru.

PennDOT spokesperson Fritzi Schreffler says it’s one of the stranger situations she’s seen with so many crashes in a short amount of time.

“It’s not uncommon for us to have a secondary crash when there’s something significant happening, especially on an interstate with the speeds,” Schreffler said.

The three hazmat situations included two fuel spills and ground fiberglass particles needing to be cleaned up.

“You always have to do defensive driving. We have to watch out for motorcycles, people that are on their phones, people who are eating, people who are putting makeup on,” Jenkins said.

Schreffler says it’s important to wear your seatbelt, pay attention to the speed limit, and not tailgate.

“Tailgating is what will often lead to a chain reaction crash because you’re simply following too quickly, so you need to allow some space in between, especially a tractor-trailer,” Schreffler said. “It takes them a long time to stop, even if they jam on their brakes.”

I-81 was shut down until 1 a.m. Thursday.

Police are continuing to investigate.