Missing Christchurch schoolgirl Marie Davis may have been the victim of foul play in a place she knew, police say.
It is the latest scenario detectives are considering as the mystery of her disappearance enters its 10th day.
Police have been searching the banks of the WaimakaririRiver, north of Christchurch, following reports that a girl was heard screaming there.
But no trace of Marie, 15, has been found.
She was last seen after being dropped off at her home in the northern Christchurch suburb of Papanui by a friend's mother on the night of Saturday, April 5.
Detective Senior Sergeant Virginia Le Bas said police were looking into whether Marie may have left her home that night and and gone somewhere else she knew, and "something untoward may have happened to her".
"We're going back to the friends' addresses looking for any clues as to where she might have gone.
"We have to explore all those avenues."
Marie's cousin and family spokesman Nick Donald said the family were "still pretty scared about everything, but being as positive as possible".
Marie's mother Janet and sister Amy were struggling most.
"Everyone is going through all different emotional stages. You're very optimistic, and then you can get angry ... It's a real rollercoaster," he said.
"We still live in hope that's she's still out there."
Searching at the river seemed to be police "just covering their bases", Mr Donald said.
"Because there's no real strong leads.
"There have been things found out at these places before in other cases."
Ms Le Bas said there was nothing yet to indicate Marie had been murdered.
"We need to exhaust every possibility and we will exhaust every possibility."
Marie's cellphone, wallet and canvas shoulder bag are still being sought.
Mr Donald said even strangers were moved by the family's plight and were helping in their own way.
"A lot of people will have kids of their own ... and to have it happen to your own would be something else altogether."
