Forensic scientists have revealed that China's second to last emperor Guangxu (1871-1908) was murdered by arsenic poisoning.

The research project started in 2003 under the national program of the Compilation of Qing Dynasty History was carried out by the China Institute of Atomic Energy (CIAE), the forensic lab of the Beijing police and the China Central Television, which planned to shoot a documentary on it.

The emperor, who died at the age of 36, was well known for trying to reform the weak feudal system of the Qing Dynasty and adopt a constitutional monarchy in 1898. But his reform failed in a coup launched by the conservative Empress Dowager Cixi, the widow of Emperor Xianfeng and aunt of Guangxu.

He was under house arrest from 1898 and died suddenly in 1908, just 22 hours before the death of Cixi. The cause of his mysterious death has aroused suspicions ever since.

Forensic experts tested two strands of hair taken from Guangxu's body and found they contained arsenic, over 2,000 times higher than that of ordinary healthy people today, said a report by the committee in charge of Qing history compilation.

They also compared Guangxu's hair with two of his contemporaries, his wife Empress Longyu and a Qing official. The arsenic found on the empress' hair was 261 times lower than Guangxu and that of the official was 132 times lower.

But some experts queried that the emperor might suffer chronic arsenic poisoning as he took traditional Chinese medicine over a long period, some of which contained tiny amounts of arsenic.

Experts managed to find a person suffering such chronic arsenic poisoning. They found Guangxu's hair contained arsenic 65 times higher than that person and, more importantly, the pattern of arsenic distribution on Guangxu's hair was different from him.

"We tested higher incidence of arsenic at the hair root of the person suffering chronic medicine poisoning than the other part of the hair. But on Guangxu's hair higher incidence of arsenic was found at the end or in the middle part," said Wang Ke, a CIAE expert in charge of arsenic testing.

Through examination on the emperor's coffin, clothes and bones, experts ruled out contamination from outside.

The arsenic level found in the clothes was lower than the hair and bones. The underwear contained higher level of arsenic than the coat. The experts believed arsenic was spread from the body to the clothes through decay.

Experts also found the cloth covering the emperor's stomach contained a higher level of arsenic than the other parts and the remaining substance in his stomach was found to have a very high level of arsenic.

The arsenic so far collected from hair, clothes and the remaining stomach substance was about 201.5 mg. An ordinary person will die of eating 60 to 200 mg of arsenic.

"We conclude that Guangxu died of acute arsenic poisoning," said the report.

But who murdered Guangxu remained a mystery.

Dai Yi, a renowned historian on Qing Dynasty, suspects it was at the order of Cixi.

"Cixi (then 74 and seriously ill) was afraid that Guangxu would regain the throne and continued his reform plan after her death," he said.

After the death of Guangxu and Cixi, a two-year-old boy named Puyi ascended the throne to be the last emperor of the Qing Dynasty. He was forced to resign in 1912 by a revolution that founded the Republic of China.