A search is under way for Callum and Jake Robinson, both aged in their 30s, who are believed to have gone missing in the Baja California region, near the city of Ensenada.
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 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."
Ms Robinson said Callum was a type one diabetic and she had concerns for his health.
"Please contact me if you have seen them or know their whereabouts," she said.
Mr Cook said it was very worrying for the family.
"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 told reporters on Thursday.
"I share the concerns of all Western Australians in terms of their welfare."
Her plea came as multiple media outlets reported that a woman had been arrested during the search for the brothers after she was found in possession of one of their phones along with a quantity of drugs.
The Department of Foreign Affairs and Trade confirmed it was helping the family.
"Owing to our privacy obligations we are unable to provide further comment," a spokesperson said.
In 2015, WA surfers Adam Coleman and Dean Lucas were murdered, believed to have been shot by gang members in Mexico's volatile Sinaloa region, before their van and bodies were burnt.
19°C