LAS VEGAS — A teenager from a Las Vegas suburb remained on the loose today amid a national manhunt and charges he killed his mother and 9-year-old brother just a day after celebrating his 16th birthday with them.

The search for Adrian Navarro-Canales entered its sixth day, and police said they were also searching at the Mexican border for the southern Nevada teen. Police discovered the bodies of his mother and younger brother in the bathroom of their Henderson apartment on Friday.

Navarro-Canales initially was named by police as a possible victim, then identified Monday as the prime suspect in the slayings. An arrest warrant said he would be prosecuted as an adult.

Henderson police investigators think the killings happened Tuesday, but the bodies weren’t discovered until Friday — the fourth time a relative and the mother’s boyfriend called to say they were worried about whether he, Elvira Canales-Gomez and Cesar Navarro were OK.

Henderson police spokesman Keith Paul said officers “found no cause to break in” during the first three visits.