Daily News/Reuters
Sararat Rangsiwuthaporn was initially arrested last week by Thai authorities.
Bangkok, Thailand CNN  — 

A pregnant Thai woman arrested on suspicion of murdering her friend with cyanide has now been charged with at least 13 counts of premeditated murder, police have confirmed.

Sararat Rangsiwuthaporn was initially arrested last week for the alleged murder of Siriporn Kanwong, Deputy National Police Commissioner Gen. Surachate Hakparn told CNN.

Police have requested arrest warrants in 14 cases of alleged murder involving Sararat, with 13 approved by the court so far and one still pending, Surachate said in a press conference on Wednesday.

In the potentially linked cases currently under investigation by police, all the victims ate or drank with Sararat in the run up to their deaths. All 14 of the deceased – as well as one survivor – were poisoned with cyanide, Surachate said.

Sararat, who was remanded in custody last week, has denied the accusations, National Police Chief Gen. Damrongsak Kittiprapas added at the same press conference.

Daily News/Reuters
Sararat Rangsiwuthaporn appeared in Bangkok's criminal court after her arrest Tuesday, where she was taken into police custody.

Police are also investigating Sararat’s partner Witoon Rangsiwuthaporn, a senior police official who held the rank of Lt. Colonel.

Earlier this week, Witoon was fired from his job as a local deputy police chief. He is also facing charges of fraud and embezzlement related to the alleged murders, Surachate confirmed.

The couple are “divorced on paper” but have maintained a relationship, Surachate said, adding that Witoon has denied any knowledge of the murders.

Police have also confirmed that Sararat is pregnant.

Speaking to CNN on Thursday, Surachate said Witoon was willing to work with investigators and is set to visit his partner in prison later in the day.

“Let’s see how much he can do or if he is really sincere,” Surachate said.

Police believe the killings may have had a financial motive, with victims allegedly lending Sararat money in the run up to their deaths and investigators probing her transactions and debts as a result.

Consumer debt is a massive problem in Thailand, accounting for nearly 90% of the country’s GDP as of 2022, according to the Bank of Thailand.

The investigation into so many murders has transfixed Thailand with local media providing daily updates.

Serial murders are relatively rare and the vast majority of perpetrators of such crimes are men.

In the United States, the FBI defines serial murder as two or more killings separated by a span of time.

Fewer than one percent of homicides during a given year are committed by serial killers, the FBI says.