There are no eyewitnesses or television images yet of the crash that led to the death of Swiss rider Muriel Furrer at the road cycling world championships, investigators in Zurich said on Monday.

The 18-year-old Furrer died from her injuries on Friday, one day after crashing on a rain-slicked forest road near Kusnacht, south of Zurich, in the junior women's race.

Police and the public prosecutor's office in Zurich jointly said in a statement the exact time Furrer crashed was not yet established.

Furrer was discovered unconscious in the forest away from the road by a race safety official, the investigators said. She was later airlifted by helicopter to the hospital.

At a news conference on Friday, officials from the International Cycling Union and local race organizers gave few details of the crash and rescue operation and cautioned against speculation.

Investigators said on Monday they had no evidence any other party was involved in the crash or saw it.

Furrer's family gave their consent for racing to continue at the nine-day championships which ended on Sunday.