NEW ORLEANS ( AP) — Two men died and 61 other people were injured Thursday in a pre-dawn pileup involving about 40 cars, vans and other vehicles on a busy interstate that crosses New Orleans, closing the route for hours both ways, police said.

Drivers said they drove into thick smoke or fog that abruptly limited visibility on westbound lanes of Interstate 10 heading across eastern New Orleans. Those who came upon the scene said they heard injured motorists pleading for assistance.

“You just hear all kinds of calls and people screaming for help,” tow truck driver Wesley Ratcliff told local broadcaster WWL-TV. In 13 years responding to wrecks, he added, “this is the worst I’ve ever seen it.”

Officer Garry Flot, a police spokesman, would not talk about possible causes.

All lanes were reopened late Thursday afternoon as the investigation continued, letting commuters head home at rush hour.

The highway is heavily trafficked, a major corridor for thousands of commuters who enter New Orleans each day from its eastern suburbs and the Mississippi Gulf Coast. Those driving the route at the time of the wrecks said they suddenly found themselves in utter darkness, unable to see the lights of cars ahead.

“I thought it was fog; my husband thought it was smoke,” Stacie Williams said. “Cars were driving in front of us and before you know it, it seemed as if they had dropped off the face of the Earth.”