German police said Sunday that a collision between a high-speed train and a herd of sheep could have been more severe had it not occurred at the mouth of the nation's longest rail tunnel.

Federal police spokesman Reza Ahmari said the location of the accident accounted for only 19 of the train's 135 passengers being lightly injured. Four people suffered fractures.

"The tunnel prevented the train cars from coming uncoupled and smashing into one another," Ahmari said Sunday.

Twenty sheep were killed in the accident, which occurred late Saturday just before the mouth of the nearly 7-mile-long Landruecken Tunnel, just south of the central city of Fulda. A Hamburg to Munich-bound InterCity Express train collided with the animals on the track.

Investigators were examining how the herd of sheep, which normally graze in pastures on either side of the tunnel, came to be on the tracks when the train came barreling through at 124 miles per hour.

The animals' owner, who gave his name only as Norbert W., told The Associated Press he believed the herd had somehow been chased.

"Sheep do not simply walk onto train tracks," he said, adding that strange dogs had been seen in the pasture several days earlier.

Officials for German railway operator Deutsch Bahn said the line would be closed for several days as repairs are carried out in the tunnel, causing delays to traffic on a key north-south axis.