UPDATE: Wednesday, Nov. 17, 7 a.m.
According to PennDot spokesman Brad Rudolph, a contractor was doing work on the Wayne Junction Viaduct. The project had water running overnight, which spilled over onto Roosevelt Boulevard.
The road should have been salted before the contractor left the scene, Rudolph said, and the contractor will handle insurance claims for the people who were involved in Tuesday morning's accident.
The original story from Tuesday follows:
PHILADELPHIA (KYW Newsradio) -- The southbound lanes of Roosevelt Boulevard are clear. A massive accident caused by 'black ice' and involving as many as 18 cars and trucks shut down the road for four hours Tuesday morning.
There was no rain or snow Tuesday morning. The air temperature wasn't cold enough for freezing conditions overnight in Philadelphia, but for a portion of Roosevelt Boulevard, the temperature on the ground certainly was.
Water sprayed down by a work crew during overnight construction froze, leaving a large, thin patch of ice, and as many as 18 cars lost control and crashed. The phenomenon is known as "black ice" or "clear ice" because it is invisible to drivers.

Thakiy, one of the drivers involved in the pile up, says he was maybe the third car from the front.
"I was in the front. I was behind only two cars. But somebody hit me, and I ended up hitting somebody because I couldn't stop. I was heading to work. My back hurt, my neck hurt. It's crazy. It's crazy," he said.
He says it was an unbelievable experience that he wasn't expecting.
"Can't go to work now," he said as a tow truck driver prepared his car to be taken away. "It's definitely inconvenient."
None of the drivers involved in the crash was expecting to start the day this way.
Anthony Elliott said he was heading into work, just a normal drive, when he hit the ice.
"Pretty nice day out today and, yeah, I wasn't expecting any water on the road or ice," he said.
As light levels increased through the morning, the size and danger of the ice patch became more apparent.

Police have been on scene talking to those drivers, getting their statements, checking out the damage.
Fortunately, there are no reports of serious injuries.