A British teacher found buried in a bath of sand in Tokyo was suffocated, Japanese police have said.
Miss Hawker started her job in Japan last October
A spokesman said they had not yet been able to confirm whether Lindsay Ann Hawker, 22, from Brandon, near Coventry, was strangled or smothered.
A post-mortem examination showed she had bruises on her face and body.
Police have issued an arrest warrant for Tatsuya Ichihashi, 28, who was seen fleeing barefoot from the flat where Miss Hawker's body was found on Monday.
A police spokesman said Mr Ichihashi approached Miss Hawker last week outside a train station and asked for English lessons.
He then followed her to her apartment where she agreed to let him in because there was another flatmate at home, police said.
While he was there, they say he drew a picture of her and wrote down his name and number.
Miss Hawker's father, Bill, who is in Japan, has said he will not rest until her killer is found.
Mr Hawker has visited her body at a funeral home and is making arrangements to return her to the UK.
Accompanied by his daughter's boyfriend Ryan Garside, he also spent about two-and-a-half hours at the flat where she lived.
The suspect fled barefoot when police arrived at his apartment
Miss Hawker's handbag, identification documents and clothes were found near her body.
Neighbours heard scraping noises coming from the fourth floor flat where her body was found, according to local media.
The police want to interview Mr Ichihashi, who lived in the apartment.
The public broadcaster NHK said that Miss Hawker, who worked at an English conversation school in Chiba, east of Tokyo, had agreed to meet Mr Ichihashi to give him an English lesson.
Staff at Nova, the company that employed Miss Hawker, told the BBC that classes at the school where she worked resumed on Thursday.
The school was closed on Tuesday and Wednesday because teachers and pupils were so upset.