Mexican authorities have arrested three men in connection with the suspected murders of two Australian surfers, prosecutors said on Friday (local time).
The surfers' burnt-out van was found with two unidentified bodies last month, but police have not confirmed the remains belong to the Australians.
The tourists, Dean Lucas and Adam Coleman, were driving in a van in the violence-plagued northwestern state of Sinaloa when they were stopped by a gang, said chief state prosecutor Marco Antonio Higuera Gomez.
The suspects, whose car flashed police-like lights to stop the van, confessed to shooting a long-haired tourist in the face when he resisted a robbery on November 21.
The robbers killed the second man, drove the vehicle to another location and "set fire to the van with two bodies inside", Higuera told reporters.
The prosecutor stressed that while the case was being investigated as a murder, the identity of the two bodies had yet to be confirmed through DNA tests.
Two other suspects are on the run. Prosecutors did not say when the arrests were made.
"These people are part of a criminal group dedicated to vehicle thefts, drug dealing and with a history of committing murders," Higuera said.
Municipal and federal police uniforms were seized from the suspects, who wore them to commit highway robberies, the prosecutor said.
Lucas and Coleman, both 33, were last reported in the Sinaloa town of Topolobampo on November 20 after arriving on a ferry from the Baja California peninsula.
The two men had driven from Edmonton, Canada, and across the United States to Mexico to join Coleman's Mexican girlfriend in the western city of Guadalajara.
Their van was discovered on November 21 on a rural road of the town of Navolato. Last weekend authorities confirmed the vehicle belonged to the Australians, raising fears about their fate.
Navolato's Mayor, Miguel Calderon, described the region as a "Bermuda Triangle" of crimes that include robberies, murders and kidnappings.
Meanwhile, more than $60,000 have been raised on the crowdfunding website www.gofundme.com to help the two men's parents travel to Mexico and take their sons home.
Australian Foreign Minister Julie Bishop voiced "grave concerns" for the young men on Monday.
The Australian Foreign Affairs Department issued a statement on Sunday on behalf of the families saying they were aware of reports the van had been located and that "a tragic event has occurred".
"The families hold deep fears for the safety of their sons but stress that they are still waiting for details to be confirmed," the statement said.
The state is home to the powerful Sinaloa drug cartel led by fugitive drug kingpin Joaquin "El Chapo" Guzman, who broke out of a maximum security prison in July.
While tens of thousands of Mexicans have been killed or gone missing in nearly a decade of drug violence, violent attacks on foreign tourists are less common.
In July 2014 the decomposing body of Franco-American Harry Devert was found with signs of strangulation in the southwestern state of Guerrero, six months after he went missing while crossing the country on a motorcycle. He had travelled from New York, hoping to reach Brazil for the World Cup.