Aviation authorities in Australia have extended a ban on flying for thousands of light aircraft already grounded for three weeks by contaminated fuel.

The authorities say scientists have been unable to identify the source of the contamination, which can cause sudden engine failure, and have ordered at least five-thousand aircraft grounded for another week.

Most charter flights, many outback air services, mail deliveries and parts of the Flying Doctor service have been halted by the ban.

Aircraft operators say they are considering taking legal action against the Mobil Oil Company, which distributes the fuel. Mobil has already offered more than ten-million dollars in compensation but the operators say their losses are much greater.

From the newsroom of the BBC World Service