Philippine authorities are preparing to send a search mission near the crater of a restive volcano after they spotted the suspected wreckage of a small plane that went missing with four people on board over the weekend.

Two Australians and two Filipino pilots were on board the Cessna 340, which lost contact after take-off from Albay province south-east of the capital Saturday morning on its way to Manila, the Civil Aviation Authority of the Philippines said.

The Australians were working as consultants for Energy Development Corp, a large geothermal power company. The company said it has deployed teams backed by helicopters and drones to help in the search.

“We will not stop until they are found,” company official Allan Barcena said.

The ABC on Monday reported the two men as Simon Chipperfield and Karthi Santhanam, who had previously worked for Australian gas producer Santos.

Mayor Carlos Baldo of Albay’s Camalig town and other officials told reporters on Sunday that an aerial search spotted the suspected wreckage, including the tail, scattered about 350 metres from the crater on the steep south-western slope of Mayon Volcano.

There was no sign of people.

A ground search was hampered by rainy weather over the weekend.

About 60 search and rescue personnel may scale the 2460-metre Mayon when the weather clears, Mayor Baldo said.

They would also need assistance from volcano experts and local officials because of the restiveness of Mayon, one of the country’s 24 active volcanoes.

“It’s a very risky operation,” Philippine Institute of Volcanology and Seismology director Teresito Bacolcol told The Associated Press.

“It’s a race against time and it’s a matter of life and death but there’s also the danger of rockfalls and volcanic lahar.”

A popular tourist attraction because of its near-perfect cone, Mayon last erupted in 2018, displacing tens of thousands of villagers.

-AP