The WA premier has described as "distressing" reports two Perth brothers have disappeared while on a camping and surfing trip in northern Mexico.

Jake and Callum Robinson, both aged in their 30s, failed to arrive at holiday accommodation in the city of Rosarito.

It's understood they were surfing and camping at the popular surfing spot Punta San Jose near the city of Ensanada.

They were believed to be travelling with Jack Carter Rhoad, who is an American citizen and is also missing.

Their mother Debra Robinson has appealed for information on social media.

"They have not contacted us since April 27 ... they are travelling with another friend; an American citizen," the social media post reads.

"Callum is a Type 1 diabetic so there is also a medical concern.

"Please contact me if you have seen them or know their whereabouts."

In a statement, Ms Robinson said the family continued to hope the brothers would be located.

"We sincerely appreciate everyone's concern and thoughts at this time. We continue to have hope that our two beautiful boys are found."

"It is a deeply distressing time for us and we ask the media to respect our privacy at this time."

Social media posts stop

A friend of the brothers, Dan, said social media updates from the pair stopped at the weekend.

"Callum lives over in America and Jake was visiting and [they] sort of posted fairly regularly about their trip up until the weekend," he told ABC Radio Perth.

"They haven't actually checked into where they were meant to be on Saturday, and no one's been able to get in contact with them since.

"I think everyone's just sort of hoping that we can spread the word for anyone that has any contacts in America or around that area that might be able to put the word out.

"I believe that Jake and Callum's parents are trying to get a flight over there now."

'Very worrying': premier

Premier Roger Cook said he was aware of the situation and described it as "really quite distressing".

"This must be very worrying for the families involved," he said.

"When we do send our young men and women overseas to enjoy that adventure holiday, they invite an element of risk.

"I understand one of the individuals has a medical condition that would need ongoing care.

"I share [the] concerns of all Western Australians in terms of their welfare."

DFAT contacted

According to an online lacrosse profile, Callum Robinson attended high school at Sacred Heart College in Perth before travelling to the United States to play college lacrosse.

Both brothers have regularly posted images of their travels to social media.

In 2015, Australian surfers Dean Lucas and Adam Coleman were murdered while travelling through Mexico in a camper van.

The Department of Foreign Affairs and Trade (DFAT) has been contacted for comment.

The Department's latest travel advice for Mexico is for people to exercise a high degree of caution due to the threat of violent crime.

The advice said Mexican government statistics show Baja California Sur and Quintana Roo have reported significant increases in drug-related violence, particularly murder.

Baja California Sur and Baja California are among the states with the highest homicide rates.