There have been emotional scenes at a temple in Beijing where relatives of passengers on board Malaysia Airlines flight MH370 gathered to mark six months since the plane disappeared.
About 30 relatives listened to a man read a poem, some crying and sitting on the floor.
Tempers flared when police tried to move people on, sparking shouting.
No trace of the Beijing-bound aircraft has been found since it disappeared on 8 March, carrying 239 people.
Based on analysis of satellite data, MH370 is believed to have ended its journey in seas far west of the Australian city of Perth.
Investigators do not know what happened to the flight, however, and finding its "black box" flight recorders is seen as key to understanding the factors behind its disappearance.
Teams are now preparing to search a 60,000 square km priority area in the Indian Ocean, using towed deep water vehicles equipped with side scan sonar, multi-beam echo sounders and video cameras.
At the moment the ocean floor is being mapped to facilitate the underwater search, which will begin later this month.
The agency co-ordinating the search says it remains "cautiously optimistic" the plane will be found.
Acting search chief Judith Zielke told the BBC that experts were continuing to refine the priority search area, based on data analysis.
"The purpose of prioritising the area and therefore the ongoing refinement is to try to cut to where we should be looking first to make sure we can locate the aircraft as quickly as possible," she said.
Earlier this month Australia said the focus would move to the south of the area, after analysis of a failed attempted satellite phone call from Malaysia Airlines to the plane found the aircraft may have turned south earlier than thought.
Experts led by the Australian Transport Safety Bureau were finalising that latest analysis, Ms Zielke said.
"What we are continuing to do is move the equipment further south from the priority area to continue to look at the ocean floor, to map the contours of the floor and understand how best to plan the search with the deep sea equipment that will commence later this month," she said.
A Dutch contractor, Fugro Survey, will carry out the deep sea search once the mapping phase is complete.
Project manager Paul Kennedy told the BBC the mapping had highlighted areas of complexity on the sea floor, which ranged in depth from 975m to around 5,500m.
This data would help when repositioning the towed underwater equipment so as to avoid obstacles on the sea floor, he said.
The underwater search is expected to take up to 12 months to complete, Australia says.
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