Authorities in western China's restive Xinjiang region have found nothing toxic in blood samples taken from victims of a wave of needle attacks, state press said on Monday.
No radioactive, poisonous or viral substances were detected in tests on 250 people who were allegedly jabbed by needles in the regional capital of Urumqi, Xinhua news agency said, quoting disease control experts.
The announcement comes after a Chinese court on Saturday sentenced three people to up to 15 years in jail over the attacks, which China's state-controlled media has said involved syringes.
The government has blamed the attacks on Muslim separatists, but has provided no evidence.
State press reports on the convictions on Saturday made no reference to separatism.
Xinjiang's mostly Muslim ethnic Uighur minority have long complained of Chinese religious and political oppression.
The mysterious assaults provoked demonstrations earlier this month by Han Chinese demanding the government improve safety in Urumqi, which has been tense since riots by Muslim Uighurs in July left nearly 200 dead, mostly Han.