Doctors have examined the bodies of the six persons who died in a Bangkok luxury hotel suite and discovered cyanide in their blood.

They claim that cyanide is the only explanation for their deaths based on the preliminary post-mortem examination.

However, more testing is being done to ascertain the "intensity" of the lethal substance and exclude any other poisons.

Cyanide residue was previously discovered by forensic examiners on the teacups used by the victims, all of whom are Vietnamese nationals, two of whom holding dual US citizenship. Police haven't identified the deceased person they believe was responsible for the poisoning, but they believe it was motivated by crippling debt.
 

According to Professor Kornkiat Vongpaisarnsin of Chulalongkorn University's Department of Forensic Medicine, the victims' internal organs turned "blood red," which is another indicator of cyanide poisoning, and their lips and nails had turned dark purple, suggesting a lack of oxygen.

The dean of the Faculty of Medicine, Dr. Chanchai Sittipunt, stated that more research was necessary to determine the exact amount of cyanide present in the deceased's blood.

"However, cyanide is the only factor that could have contributed to their deaths, based on our observations, internal organ checks, and detection of cyanide in the blood during the screening test," he said to reporters.

Late on Tuesday, housekeepers at the Grand Hyatt Erawan hotel in the Thai capital discovered the corpse.

By then, according to investigators, they had been dead for twelve to twenty-four hours.

International news outlets covered the mystery surrounding the startling discovery.

Srettha Thavisin, the prime minister of Thailand, stressed that the deaths were the consequence of a "private matter" and that there was no indication that the public was in danger as she requested an immediate investigation into the case.

Since then, police have started piecing together what might have occurred.

According to officials, two of the six victims had lent "tens of millions of Thai baht" to one of the deceased for financial motives. The equivalent of ten million baht is around $280,000 (£215,000).

Gen. Noppassin Poonsawat, the deputy commander of police in Bangkok, stated earlier on Wednesday at a press briefing that the gang had individually checked into the hotel over the weekend and had been given five rooms—four on the seventh floor and one on the fifth.

They were supposed to check out on Monday, but they didn't show up.

Vietnamese nationals Thi Nguyen Phuong, 46; her husband, Hong Pham Thanh, 49; Thi Nguyen Phuong Lan, 47; and Dinh Tran Phu, 37, are among the four victims.

Dang Hung Van, 55, and Sherine Chong, 56, are citizens of the United States.

In addition to expressing sympathy, the US State Department stated that it is "closely monitoring" the situation. According to Mr. Srettha, Thai officials are receiving investigative support from the US Federal Bureau of Investigation.

What do the police think may have occurred?

Although the reason behind the crimes is unclear, authorities claim that two of the six lent a significant sum of money to a group member who had not been reimbursed.

On Monday afternoon, according to the police, all six victims congregated in the fifth-floor room.

The lone occupant in the room at the time, Ms. Chong, accepted the food and tea that the party had ordered when it was brought to the room at approximately 14:00 local time (08:00 BST).

A waiter offered to make tea for the guests, but Ms. Chong declined, according to the deputy police chief. Authorities added that the waitress remembered her as someone who "spoke very little and was visibly under stress."

Finally, the waiter left the room.

Then, between 14:03 and 14:17, the remainder of the group started to pour into the room. The six people inside the room are thought to be the only ones who entered, and according to the police, the door was shut from the inside.

According to the police, there were no indications of a struggle, robbery, or break-in. All six tea cups had residues of cyanide in them later on.

Plates of unfinished food, some still wrapped in cling wrap, are shown on a table in the room in photos that the police have released.

Police recognized the seventh name on the group's hotel reservation as belonging to one of the victims' younger sisters. She is not connected to the incident, according to authorities, and departed Thailand last week for the Vietnamese beach city of Da Nang.
 

Thi Nguyen Phuong and Hong Pham Thanh were a couple who ran a road construction company and gave money to Ms. Chong so she could invest in a hospital development project in Japan, according to relatives who spoke with authorities.

Police believe that Mr. Tran, a Da Nang-based makeup artist, was also "duped" into investing money.

According to BBC Vietnamese, Mr. Tran's mother Tuý said that her son left for Thailand on Friday and contacted home on Sunday to let her know he needed to stay until Monday. His family hadn't heard from him since then. On Monday, she called him once more, but he did not pick up.

Mr. Tran was recruited by Ms. Chong to do her own makeup for the trip, a student of his told BBC Vietnamese. Vietnamese media was informed last week by Mr. Tran's father, Phu, that his son had been recruited by a Vietnamese woman to travel to Thailand.

The six dead were found just one day after Thailand opened up its visa-free travel policy to visitors from 93 nations and territories in an effort to boost the country's tourism sector.

How hazardous is cyanide, and what is it?

Cyanide is a very poisonous, quickly acting chemical that has the potential to be fatal. Nature and the goods we use and consume include trace amounts of cyanide. However, at higher concentrations, it is a well-known poison that has been employed as a chemical warfare weapon due to its quick acting and extremely deadly characteristics.

It can exist as a colorless liquid or vapor or as a crystal. Cyanide can enter the body through the skin, be inhaled, or be consumed in the form of food or drink.

In a matter of seconds, ingestion of excessive quantities of cyanide can result in lung damage, unconsciousness, and even death, as per the Centers for Disease Control and Prevention (CDC).

Cyanide is extremely dangerous even at lower dosages, resulting in nausea, vomiting, shortness of breath, and chest discomfort.

Although not everyone can smell it, cyanide can have a "bitter almond" scent, however it doesn't always.