DAYTON, Ohio (AP) _ Five people have been shot to death since Thursday in what police called a ''joy killing'' spree.

The latest victims, a man and a 16-year-old girl who were shot in the head, were found Sunday in a former landfill.

The shootings ''started out as robberies, but it became easier and we think it turned into joy killing,'' Sgt. George Hammann said. The assailants ''were like a shark - once they tasted blood they couldn't stop.''

Police believe the deaths discovered Sunday are linked to a string of holdups in which three people were slain and two wounded, Sgt. Larry Grossnickle said. He would not elaborate on the link except to say that the latest victims ''were found using information gained out of the investigation of the other slayings.''

Police arrested two juveniles and two adults on Saturday after they allegedly were seen taking items from the car of a man found shot to death in his ransacked home. Their names were not released pending filing of charges.

There was no additional comment from investigators today; several telephone calls were not returned.

There was no word how long the victims found Sunday had been dead. Autopsies were being conducted on both victims, said a woman who answered the phone at the office of Montgomery County Coroner James Davis. She would not give her name.

On Thursday, a woman was fatally shot seven times while standing at a pay phone. On Friday, a man was found shot to death in a wrecked car. On Saturday, two people were wounded during an attempted robbery at a store.

Grossnickle said police believe that only the two victims found on Sunday were known to the assailants.