Police concluded their investigation into Thailand's worst suspected serial killer on Friday, handing prosecutors the case against a woman accused of a spate of cyanide poisonings.

Fourteen victims died and one survived an alleged murder spree that spanned eight years, police said, announcing that they would file the case to the Attorney General for prosecution on Friday.

Sararat Rangsiwuthaporn, 36, is facing about 80 criminal charges, including 14 counts of premeditated murder -- a record in Thai criminal history, police said.

"Sararat is charged with premeditated murder in all 14 cases, which carries the death penalty," Anek Taosuparb, deputy commander of the Crime Investigation Division, told reporters.

"This is a historic case in Thailand. Even Jack the Ripper from the UK did not kill this many," Deputy Police Chief Surachate Hakparn said, referring to the pseudonymous killer of at least five women in London's East End in 1888.

Other charges include cyanide poisoning, forgery and theft, the Reuters news agency reports.

Surachate said Thailand will  tighten regulations on access to cyanide, according to Reuters.

Sararat is pleading not guilty to the charges, according to police. She has denied committing murder but has confessed to using cyanide, Reuters says, citing police.

Authorities said the alleged murders were committed with a financial motive and that the suspect had an addiction to online gambling.

She is alleged to have swindled a collective total of more than $140,000 out of her victims before poisoning them with cyanide.

Thai officers interviewed more than 900 witnesses and examined 25,000 documents.

Sararat won't be eligible for bail because police say she would pose a danger to the public.

Sararat had a miscarriage in prison earlier this week and was sent to hospital, local media reported.

Police denied that their interrogations contributed to the miscarriage.

Her former husband, a high-ranking policeman, is also facing a criminal charge related to covering up a crime.

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• Serial Killer