People in Thailand are mourning the children and teachers killed in a bus fire during a school trip earlier this week. Families of the victims are demanding answers.

A mass funeral began on Thursday in central Uthai Thani province where the school trip originated. Families and government officials offered flowers to the victims. Forty-five people were on board the bus. Twenty children and three teachers died.

A woman who lost her 6-year-old granddaughter said that she wants justice for her grandchild as well as compensation.

The bus was running on natural gas. Police say the initial investigation has found a gas leak. The driver was charged with reckless driving and failing to help passengers at the scene.

Thailand's education ministry has suspended school field trips nationwide until safety measures are reviewed.