The FBI lab forensic reports of the viscera sample of Sunanda Pushkar, late wife of Indian politician Shashi Tharoor, have ruled out the angle of death by polonium or any other radioactive substance.

Delhi Police Commissioner B.S. Bassi on Wednesday said that radiation levels in samples drawn from Sunanda Pushkar - Congress leader Shashi Tharoor's wife who died in a Delhi hotel under mysterious circumstances - were within safety norms.

"We have received the FBI's forensic report by email. A detailed report is still awaited. Once we get the full report, the medical board would examine it," Bassi told reporters, IANS reported

"Radiation levels in the samples were within the prescribed safety norms," he said.

Bassi said Delhi Police would proceed further after a medical board gives its opinion on the Federal Bureau of Investigation (FBI) anaylsis report.

Reacting to the development, All India Institute of Medical Sciences forensic department head Sudhir Gupta said some poisons cannot be detected though these can cause death.

Sunanda Pushkar's viscera samples were sent to the US after AIIMS doctors said that Indian laboratories lacked the facility to identify the poison that was suspected to have caused her death.

Pushkar was found dead in a luxury hotel in Delhi on January 17, 2014, under mysterious circumstances. Police registered a murder case on January 1, 2015.