It's been two weeks since a section of Alcoa Highway collapsed. For some 40 hours, it caused traffic headaches for thousands of East Tennessee drivers.

Before the collapse, KUB had been working nearby, fixing a broken water main.

Authorities say it's still unclear whether that leaky pipe lead to what looked like a "sinkhole," calling it a "chicken and egg" situation.

RELATED: TDOT: All lanes of Alcoa Highway open following sinkhole repairs

Bob Hatcher, UT professor of geology, said sinkholes happen when groundwater eats away at limestone, forming underground caves that can eventually cave in.

"This is not unique to East Tennessee. These occur in many places in the eastern United States, so sinkholes are not all that uncommon, but we have our share of them here," Hatcher said, gesturing to a map of East Tennessee denoting wide swaths of areas susceptible to sinkholes.

Some people have asked 10Listens whether a collapse like this could occur again.

"The collapse of these things is a random thing. You can't predict it because we don't know where all the underground drainages are in this area," Hatcher said.

However, Hatcher said, what happened two weeks ago on Alcoa Highway may not technically be a sinkhole.

"This one on Alcoa Highway that we're talking about, is one that may or may not be natural," Hatcher said. "It may be a man-made situation where a lot of foundation material under the road may have been washed out by a leaky water main."

KUB said 30 workers spent more than 400 hours, combined, fixing the broken water main.

TDOT filled in the sinkhole and fixed the road.

Spokespeople with both KUB and TDOT said Wednesday that even now, two weeks after the incident, it's not clear - nor may it ever be clear - whether the leaky pipe caused the collapse or whether a sinkhole caused the pipe to break.

"In this case, while KUB did work quickly, crews were actually able to take advantage of TDOT closing down the entire roadway, and excavated even more of the water main than was necessary to complete repairs," a KUB spokesperson told 10News. "This additional excavation and time enabled the crews to inspect and replace more water main as a precautionary measure against future breaks."

As for the filling of the sinkhole and repair of Alcoa Highway, a TDOT spokesperson wrote, "Sinkholes can often be difficult to detect but we monitor roadways across the region. Unfortunately this is an area of the state where we do get sinkholes from time to time."

TDOT engineers use THESE GUIDELINES when handling sinkholes.

"Sometimes these things happen catastrophically," Hatcher said.

It's rare for somebody to be injured by a sinkhole, Hatcher said, but when they happen below man-made structures, the resulting damage can cost people time and money.

KUB said an initial estimate for the cost of the water main repair is about $25,000.

TDOT's estimate on the cost of repairing the Alcoa Highway sinkhole is $177,057.