A nine-vehicle pileup inside a tunnel on the Tohokudo Expressway in Ichinoseki, Iwate Prefecture, early Thursday resulted in injuries to six people, police said.

The injured were taken to a hospital after the accident, which occurred in the 1,002-meter Ichinoseki Tunnel at around 7:45 a.m., they said.

Police are investigating the cause of the pileup, which took place about 100 meters from the tunnel's entrance, highway patrol officers said. They added that traffic on the expressway was twice its normal volume because of the Golden Week holidays.