6 people are reportedly dead, with at least 3 confirmed. 7 people were believed to be missing, with 2 injured. Two cars were said to be trapped under the rubble.
Japanese media is reporting that several cars were on fire, and several charred bodies have been pulled from the wreckage.
Several media outlets reported that onlookers felt the ground shake before the collapse.
Scores of motorists witnessed the collapse, and 2 women recieved minor injuries while attempting to flee.
“When I was driving in the tunnel, concrete pieces fell down suddenly from the ceiling,” one man told public broadcaster NHK. “I saw a crushed car catching fire. I was frightened, left my car and walked for about an hour to get out of the tunnel.”
Officials on the scene did not know the nature of the collapse, but some had indicated that a mudslide had caused the devastation.
The tunnel, 50 miles west of Tokyo, is in Yamanashi prefecture, and is referred to as the Sasago tunnel, part of the Chuo expressway, which is the major east west roadway connecting the capital to Western Japan.
Firefighters had initially determined that several charred bodies were found in a white van, crushed under the weight of the collapsed concrete. The van was ablaze, and firefighters had trouble putting it out because of the thick smoke.
Rescue attempts had to be halted at one point, as officials feared another collapse.
Here is a closed circuit TV video of the collapse, as provided by the Guardian UK.
Reported by Jim Donahue