JOHANNESBURG >> At least 38 girls and young women were killed in a crash while travelling to Swaziland’s most famous traditional festival, a rights group said on Saturday.

About 20 others were injured when the truck they were in collided with another vehicle on Friday, the Swaziland Solidarity Network said in a statement. The young women and girls were travelling on the back of an open truck, the rights group said.

The girls and young women were on their way to the Swazi king’s royal residence for the annual reed dance.

About 40,000 young women participate in the eight-day reed dance ceremony in which they sing and dance, usually bare-breasted, as they bring reeds to reinforce the windbreak around the royal residence. During the reed dance, the king often selects one of the young women to become one of his wives. Swaziland is polygamous and the king has more than a dozen wives.

“We all have heard about the dark cloud that has befallen the ‘imbali,'” said King Mswati III, using the Swati language word for flower, used to refer to the groups of women dancers. Speaking Saturday at the opening of an international trade fair in Swaziland’s economic center Manzini, the king promised that the affected families would be compensated. He added that an investigation into the accident was underway.

Police in Swaziland, a small mountainous country of 1.4 million people bordering northeastern South Africa and Mozambique, discouraged reporting on the accident, said the rights group. Press photographers were prevented from taking pictures at the scene, said a Swazi journalist who insisted on anonymity for security reasons. However some people managed to take photographs of the aftermath of the crash with their cell phones.

A high-ranking police officer contacted by The Associated Press refused to comment on the accident, saying the matter was related to the “highest authority,” and no details could be disclosed to the media.

“You don’t hide a death,” said Lucky Lukhele, spokesman for the Swaziland Solidarity Network. Members of the Swaziland Defense Force alerted the rights group to the accident, Lukhele said, adding that he expected the death toll to rise.

The females were traveling on a highway between the Swazi cities of Mbabane and Manzini, when the truck carrying them smashed into a vehicle and was then hit in the rear by a second truck, the Times of Swaziland reported.

“We were about 50 on board the first truck that smashed into the Toyota van,” said Siphelele Sigudla, 18, a survivor quoted by the Times of Swaziland.

Swaziland is Africa’s last absolute monarchy, ruled by King Mswati since 1986. Swaziland held parliamentary elections in 2013, but many international observers say the electoral process is manipulated to prolong the king’s hold on power. According to the king, Swaziland’s image has been damaged by misinformation.

The country has one of the world’s highest rates of HIV infection.