There are grave concerns for two Australian brothers who went missing during a surfing trip in Mexico, after local investigators found an abandoned ute and tents believed to be linked to their disappearance.
A search is continuing for Perth siblings Callum and Jake Robinson, both in their 30s and believed to be missing in the Baja California region, near the Mexican city of Ensenada.
The alarm was raised after the pair did not check in to their accommodation.
Anthony Albanese said Department of Foreign Affairs and Trade officials had been in contact with the family following the disappearance.
"This is a really concerning situation," the prime minister told Seven's Sunrise program on Friday.
"Our embassy in Mexico is working with local authorities as well to try to ascertain what has happened here.
"We certainly hope that these brothers are found safely but there is real concern about the fact that they've gone missing. Their mother is obviously very distressed about this and we just hope for a positive outcome."
Their mother Debra Robinson has appealed for help to find her sons on Mexican social media, saying she had not heard from them since Saturday.
"They were due to book into an Airbnb in Rosarito after their camping weekend but they did not show up," she wrote.
"Callum is a type one diabetic so there is also a medical concern. Please contact me if you have seen them or know their whereabouts."
Ms Robinson said an American man travelling with the brothers was also missing.
It comes as Mexican authorities said three people had been taken in for questioning in relation to the disappearance.
Baja California state chief prosecutor María Elena Andrade Ramírez would not confirm whether they were suspects or witnesses but said abandoned tents found by investigators linked them to the missing men.
Local reports said authorities had detained a woman and two men, with the woman found with a mobile phone that contained a photo that looked like one of the missing brothers.
A white pick-up truck related to the investigation had also been located, the prosecutor said.
Ms Andrade Ramírez told a press conference in Mexico that "all lines of investigation remain open at the moment", with drug cartels known to operate in the Baja region.
While the Australian government places a lower risk on Baja California than nearby states such as Sinaloa, travellers are advised to exercise a high degree of caution "due to the threat of violent crime".
DFAT confirmed it was providing assistance to the Robinson family.
"Owing to our privacy obligations we are unable to provide further comment," a spokesperson said.
Opposition foreign spokesman Simon Birmingham also expressed concern for the missing brothers.
"Our hearts really do go out to the parents of Jake and Callum Robinson and all of their loved ones, who would be suffering immense stress at this point in time," he told Sky News.
"Their disappearance would be something that is taken extremely seriously by Australian authorities."
West Australian Premier Roger Cook said the situation was not "looking great".
"This must be horrible for the Robinson family and for everyone in the community who knows those boys," he said.
"We just want to bring them home."
