Police will summon 31 people, including actress Preechaya "Ice" Phongthananikorn, next week to acknowledge charges that they allegedly purchased cyanide for wrongfully intended purposes, according to deputy national police chief Pol Gen Surachate Hakparn.
The Department of Industrial Works (DIW) has filed reports with the Crime Suppression Division against 31 people who are believed to have traded and purchased cyanide illegally, in contravention of the Hazardous Substances Act, he said.
They include Ms Preechaya and the alleged serial killer Sararat "Aem Cyanide" Rangsiwuthaporn, who is accused of murdering 14 people as well as one attempted murder.
Ms Preechaya was said to have bought cyanide from the same source as Ms Sararat to use as a pesticide.
Charges related to the purchase of a chemical compound (cyanide) for wrongful use carry a maximum sentence of three years and a fine of up to 300,000 baht, or both, Pol Gen Surachate said.
"Officers at the Crime Suppression Division will summon all 31 people to acknowledge their charges, and they will conduct a probe to determine whether officials from the DIW were involved in any misconduct," he said.
This follows the arrest of Ms Sararat, who is suspected of poisoning her victims with cyanide.
Officers have expanded their probe into the case and found that cyanide was imported, traded and purchased for wrongful purposes, leading to the DIW's lawsuit.
In June, Pol Gen Surachate said Ms Sararat faces more than 75 charges -- including premeditated murder, attempted murder, and theft causing death and forgery in 15 cases dating from 2015 to this year.
The 15 cases were spread over seven provinces -- Nakhon Pathom, Samut Sakhon, Kanchanaburi, Phetchaburi, Ratchaburi, Udon Thani and Mukdahan.
Police wrapped up the investigation into Ms Sararat after questioning more than 900 witnesses over three months, he added.
Jullapong Thaveesri, the DIW's director, said in May that 14 firms can legally import up to 80 tonnes of cyanide per year and individuals who used more than 100 kilogrammes over the past six months must report it to the DIW.