Officials still do not know what caused the sinkhole.
Engineers called for a sonar unit to scan the 30-foot-wide, 1-1/2-foot-deep depression to find out what caused it.
The highway was closed from Exit 408 to Exit 414 in Pender County and traffic to Wilmington was rerouted onto U.S. 117 through Castle Hayne.
"It's bigger than a dip but it ain't no crater,'' said one motorist who had seen the road. "The pavement is still there.''
DOT division engineer Allen Pope said the depression was the type of problem that he has seen when underground drainage systems leaked and washed away supporting soil and caused pavement to sink.
"We know there is none of that type of structure in this area,'' Pope said.
Pope said there were sink holes in the general area when the highway was built in the early 1980s, but most were filled with grout or other material. He said limestone rock under the road could have eroded and weakened support of the highway.
"I guess asphalt has bridged over whatever is down there. I've seen where a sanitation manhole may have developed a leak and created a cavity under the pavement of the size you could put a Volkswagen in, but nothing of this caliber.''
The problem was reported to the Pender County emergency dispatcher by a motorist who drove through it and called 911 at 4:30 a.m. Friday. The Highway Patrol closed the lanes and called DOT. No vehicles were stuck in the trap, but there were scratch marks showing some hit it running fast.
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