The bodies of Maria Jose Alvarado, 19, and her sister Sofia, 23, were found buried near a river in the mountainous region of Santa Barbara in western Honduras, said Leandro Osorio, head of the criminal investigation unit.
Police suspect that Plutarco Ruiz, Sofia's boyfriend, shot and killed the elder sister in a fit of jealousy after seeing her dancing with "another person or something similar," then shot Maria Jose and buried the bodies, Osorio said.
"This is the main hypothesis we have for this crime, based on the witnesses and investigations we've done," he added.
Police took Ruiz and Aris Maldonado into custody on Tuesday, confiscating two pistols and their pick-up truck and identifying them as the homicide's main suspects, he said.
On his Facebook page, Maldonado lamented "these very difficult and unjust moments of life" but did not make reference to any details of the double homicide. Ruiz has yet to comment publicly on the allegations.
Alvarado, a student who aspired to become a career diplomat, had been due to take part in the Miss World pageant that starts on Thursday and culminates in the final in London on Dec. 14.
The sisters went missing Nov. 13, when they were seen leaving a birthday party for Ruiz at a local water park in a car without a license plate in Santa Barbara, a coffee-growing region where drug gangs are active.