UPDATED: 2/12/14 6:00 pm ET - adds photo gallery
Eight vehicles in the Skydome area of the National Corvette Museum in Bowling Green, Ky., were swallowed by a massive sinkhole at about 5:40 a.m. today, the museum said.
The sinkhole is estimated to be about 40 feet wide and 20 to 30 feet deep, the museum said in a statement.
Two of the vehicles -- a 1993 ZR-1 Spyder and a 2009 ZR1 Blue Devil -- were on loan from General Motors.
The other six vehicles, owned by the museum, included a 1962 black Corvette; 1984 PPG Pace Car; 1992 white 1-millionth Corvette; 1993 40th anniversary Corvette; 2001 Mallett Hammer Z06; and the 2009 1.5-millionth Corvette.
The museum said engineers would assess the situation today and the museum was closed this afternoon. No injuries were reported.
Museum spokesman Bob Bubnis said the museum at this time has been unable to determine if the vehicles are salvageable.
"We don't know yet," he said. "Some of the damage is varied, but what you see in the picture is what's there. Honestly, we don't know what kind of shape the (vehicles) are in."
Bubnis said the museum still is waiting for structural engineers to determine when it's safe to go back inside the Skydome area.
The museum is about a quarter mile from GM's Bowling Green Assembly Plant, where Corvettes have been made since 1981.
That region of south central Kentucky contains many caves and sinkholes, known as "karst" topography. Mammoth Cave National Park is about 20 miles from Bowling Green.
"It's not uncommon for us to see sinkhole collapses," said city spokeswoman Kim Lancaster. "Most are significantly smaller than the one we have today."
Bowling Green city hydrologist Tim Slattery said when the museum was constructed, builders "did do their due diligence" on the area's geography. But sinkholes can develop over time, as water goes underground and carries soil with it, he said.
The value of the damage was not immediately known, as most are one-of-a-kind collector cars with no similar sales figures to use as comparison, according to Sam Murtaugh, marketing director at Mecum Auctions of Wisconsin.
"How do you even begin to place a value on the 1 Millionth Corvette built?" Murtaugh said in an e-mail. "It's irreplaceable."
Dave Chrisley, president and co-founder of the Bowling Green Assembly Corvette Club, which was started by plant workers, said he believes the cars on loan from GM were the most valuable -- especially the Spyder.
"You'd have to auction it to even put a price on it," said Chrisley. "I couldn't even give you a ballpark. It was a concept car."
The museum's Facebook page was filled with comments from devastated auto fans, including one suggesting that flags be lowered to half-staff "to honor the fallen vettes."
Reuters contributed to this report.