British police have begun draining three lakes as they investigate the murder of a Saudi student who was stabbed to death last week in an apparent anti-Muslim attack.
They also have released a description of a suspect who was seen on the trail where 31-year-old Nahid Almanea was stabbed 16 times on Tuesday last week.
Police said the man appeared to be aged in his late teens-to-30 and tanned.
“He had very black, thick hair which was quite short and a two-to-three-inch mop style on top," Detective Steve Worron was quoted as saying by local media.
He was wearing baggy trousers and a "distinctive jacket which is described as being an Italian designer item" and mustard in colour.
Police also are looking for a man who was wearing a red hooded top and seen running near the murder scene about 10.50am.
Almanea had been walking from her home to an English institute when she was attacked on the Salary Brook Trail in Colchester, an hour north of London, about 10.40am.
She was wearing an abaya and headscarf at the time, causing police to consider her religion as a motive for the murder.
She had lived in England for less than a year while studying for a PhD, the BBC said.
Her body was returned to Saudi Arabia on Saturday, when a funeral also was held. 
Police have drained a nearby fishing lake and plan to do two more in the search for a weapon or bloodied clothing.
No "knife or other bladed weapon with a proven link to the murder of Nahid" had been found, police said.
Police have not ruled out a possible link with the March murder of James Attfield, who had brain damage and was stabbed 102 times at a park near where Almanea was murdered, although the cases so far have been kept separate.
"We have now had two knife murders in Colchester in less than three months where the motive for the attacks remains unknown,” the BBC quoted Worron as saying.
"Against that background, we would advise everyone in the town to remain vigilant".