The US Federal Bureau of Investigation (FBI) may be allowed to take part as an observer in the investigation into the death of Hollywood star David Carradine, provided it submits an official request first.

The 72-year-old actor was found dead at Bangkok's Nai Lert Park Hotel last Thursday.

Under the law, the FBI can submit a request to participate in the probe with the Office of Attorney General (OAG). Sirisak Tiyaphan, head of the OAG Foreign Litigation Department, said yesterday that foreign agencies were usually only allowed to observe cases.

"They may supply evidence available overseas, but can't launch their own investigation," he explained.

Sirisak also ruled out any suggestion that the FBI can arrest any suspects in Thailand.

"All arrests come under the jurisdiction of the Thai police," he said. "The Lumpini police station is in charge in this case."

Lumpini police station's superintendent, Colonel Somprasong Yentuam, said his team was still waiting for information from the Scientific Crime Detection Division.

"The results of tests related to the crime scene will be issued in a week," he said.

Earlier reports have said that Carradine might have accidentally killed himself through auto-erotic asphyxiation.