HANOI, Vietnam >> Vietnamese authorities said today that they are investigating the self-immolation of the mother of a prominent blogger who is in police custody awaiting trial on charges of conducting propaganda against the state.

Foreign Ministry spokesman Luong Thanh Nghi said in a statement today that 64-year-old Dang Thi Kim Lieng set herself on fire Monday and died on the way to a hospital. Nghi’s comments were the government’s first official response to the incident, and confirmed earlier police accounts.

Lieng’s death was not reported in state-controlled media.

Nghi said the case was under investigation.

Lieng’s daughter, Ta Phong Tan, is a former police officer who wrote a blog that addressed social justice issues. She was arrested last September.

She and two other bloggers — all members of the outlawed Free Journalists Club — are awaiting trial on accusations that they wrote hundreds of articles that “distorted and opposed” the communist government.

Their trial was planned for next week, but lawyer Ha Huy Son said he was told by the court Friday that it has been postponed. No reason was given and no new date has been set, he said.

The United States has expressed deep concern over Lieng’s death and called on the communist government to release all three bloggers.

If convicted, they face up to 20 years in prison.