Missing beauty queen found dead

• María José Alvarado Muñoz was set to head to London to participate in the pageant


• One of those arrested is beauty queen's sister's boyfriend, family tell police


• NEW: Congressman recounts how he knew sisters and boyfriend as students


• NEW: The boyfriend was a temperamental student but also quiet and humble

(CNN) -- A Honduran beauty queen and her sister were found dead Wednesday, police said, and the sister's boyfriend and another man have been arrested.

The bodies of María José Alvarado Muñoz, the reigning Miss World Honduras, and her sister, Sofia Trinidad Alvarado, were found buried in a shallow grave in a mountainous area beside a river, Honduran authorities told CNN affiliate Televicentro.

The bodies of the sisters, who had been missing for several days, were found on top of each other, Santa Barbara Mayor Juan Alvarado told the outlet.

Plutarco Antonio Ruiz Rodriguez and Aris Valentin Maldonado Mejia are now in police custody, and investigators believe more people are involved in the sisters' deaths, Police Deputy Commissioner Rolando Casco Torres told Televicentro.

Ruiz was Sofia's boyfriend, police say, according to CNN en Español.

Search for motive in beauty queen death

The sisters disappeared Thursday night after going to a spa for a birthday party for Ruiz in Santa Barbara, northwest of the capital of Tegucigalpa, police told CNN en Español.

Ruiz is suspected of killing the two sisters, said Leandro Osorio, chief of the National Bureau of Criminal Investigation.

Ruiz also "is considered the person who was most in contact" with the victims, Casco added, according to Televicentro.

Edgardo Casana, a congressman from Santa Barbara, said the two women, their other sister and Ruiz were all students of his when they were younger. In fact, Casana, a teacher, said he knew the three sisters' family well, and that Ruiz was also in a youth soccer league with Casana's children, he said.

"I'm dismayed by what happened," Casana told the CNN affiliate.

As a boy in Casana's class and in the soccer league, Ruiz was temperamental but also quiet, humble and gentle, Casana said. Ruiz's nickname was Paco, the official said.

In fact, Casana just saw Ruiz on Monday in Santa Barbara, the congressman said.

"We talked about soccer," Casana said.

Alvarado, 19, was supposed to leave for London soon to participate in the Miss World pageant, police said.

Their family reported the women's disappearance on Saturday. Their mother, Teresa Muñoz, initially believed her two daughters were kidnapped.

Eduardo Zablah, director of the pageant in Honduras, told Televicentro that Alvarado and her sister were last seen getting into a vehicle after attending a party last week.

The young woman was to be among the contestants from more than 120 countries who arrive in London this week for early rounds of the Miss World pageant. The final round is scheduled for December 14.

A student from Santa Barbara, Honduras, Alvarado beat 18 contestants to win the Miss World Honduras crown in April.

In her profile on the pageant's website, she described herself as "dedicated" and said she would someday like to go into government, specifically as a diplomat for her country.

She also said that she liked playing volleyball and soccer, eating Honduran food and performing the country's traditional punta dance.

Julia Morley, the chairman of the Miss World pageant, said contestants will hold a special service Sunday to honor Alvarado and her sister and offer prayers for their families.

"We are devastated by this terrible loss of two young women, who were so full of life," Morley said.

Honduras has the world's highest murder rate, the United Nations reported earlier this year, with 90.4 homicides per 100,000 people in 2012.

Journalist Elvin Sandoval, reporting from Tegucigalpa, Honduras, and CNN's Catherine E. Shoichet and Greg Botelho in Atlanta contributed to this report.