Police are still questioning a man on suspicion of murder, after the burnt body a 16-year-old girl was found in an alley, with fatal stab wounds in the head and face.
Lancashire Police said a post-mortem examination showed Sasha Marsden, from Blackpool, died as a result of "significant stab wounds".
Ms Marsden lived with her parents in the Staining area of the town and was in the first year of a childcare course at Blackpool and The Fylde College.
Her body was found in an alley after 9pm on Thursday behind Kirby Road, a few blocks off the Promenade on the resort's South Shore.
Police said a 22-year-old man and a 20-year-old woman, both from Blackpool, were arrested nearby a short time later.
The woman has since been released without charge, but police say they have been given more time to question the man.
A police spokesman said: "Following the death of Sasha Marsden, a Home Office post-mortem examination has been carried out and has found that Sasha died as a result of receiving significant stab wounds to the head and face.
"It also showed that attempts were made to set the body on fire and this was after Sasha had died.
"Detectives have been granted a warrant of further detention in respect of a 22-year-old man and he will be detained at Blackpool police station for a further 36 hours."
On Friday, crime scene investigators did a forensic search of the alley and at the Grafton House bed-and-breakfast hotel on Kirby Road.
Mandy Pritchard, head of the college's school for society, health and childhood, said she was "a friendly, considerate individual who cared about her fellow students".
Numerous tributes were paid to the youngster on a Facebook page set up in her memory.