Authorities have reportedly made a further grim find in their hunt for two Australian brothers and a friend who are missing in Mexico.

Local media is reporting the missing trio’s ute has been found burned out near the city of Ensenada, in the Baja California region.

Friday’s discovery follows earlier reports that three people – two men and a woman – had been arrested in connection with the search for Perth siblings Callum and Jake Robinson, both in their 30s, and their American friend Jack Carter Rhoad.

According to local reports, the woman – the partner of one of the men – was found with a mobile phone that contained a photo that looked like one of the missing brothers. However, other accounts suggest the trio was only questioned.

“Municipal police located a pickup-type on fire belonging to one of the three missing tourists on the afternoon of this Thursday, May 2,” Mexico’s Patrulla 646 reported.

“The location was in the area of a ranch located in the Santo Thomas delegation. The ranch owner found the unit fully calcified (burned) while touring the area.”

A check of the vehicle’s VIN reportedly identified it as the Chevrolet Colorado belonging to one of the three missing surfers.

According to other reports in Mexican media, the ongoing search has also turned up the missing surfers’ tent. Evidence of a struggle, including bloodstains, was found inside.

None of the three men has been heard from in several days, with the alarm raised after the brothers failed to check in to an Airbnb after their surf trip to K38, south of Rosarito Beach. Callum Robinson was also said to be due back to work in San Diego, where he lives, but has not shown up.

Prime Minister Anthony Albanese said Department of Foreign Affairs and Trade officials had been in contact with the brothers’ family.

“This is a really concerning situation,” Albanese 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.”

Foreign Minister Penny Wong said Australian Federal Police were supporting local authorities in the search.

“The thoughts of all of us are with the families of the missing men. We are obviously deeply concerned, deeply worried,” she said.

The men’s mother, Debra Robinson, appealed on Mexican social media sites for help finding them. She has not heard from them since Saturday.

“They are travelling with another friend, an American citizen,” she wrote.

“They were due to book into an Airbnb in Rosarito after their camping weekend but they did not show up.

“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.”

The area where the men are missing is in the grip of a turf war between rival drug cartels.

A search group called Colectivo Una Nación Buscando (Collective One Nation Searching) said there were almost 18,000 missing people in Baja California – a jump of about 4000 in two years.

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.”

Western Australian Premier Roger Cook said the brothers’ disappearance was distressing.

“When we do send out young men and women overseas to enjoy that adventure holiday, they invite an element of risk and this is really quite distressing,” he  said on Thursday.

“I share the concerns of all Western Australians in terms of their welfare.”

-with AAP