( CNN ) -- A missing University of Florida student 's backpack was found at the residence of a suspect , whose car tested positive for blood , Gainesville police said Saturday . The developments came as authorities continued searching for Christian Aguilar , 18 , last seen September 20 . At a court hearing Saturday , a judge denied bail for Pedro Bravo , 18 , charged with first-degree murder in Aguilar 's apparent death . Aguilar 's backpack was found hidden inside a suitcase in Bravo 's closet , police spokesman Officer Ben Tobias said in a statement explaining what led authorities to charge Bravo with murder . Blood found in several locations in Bravo 's vehicle will undergo an expedited analysis and be compared against known DNA samples of Aguilar , Tobias said . Bravo changed his account of what happened `` after being confronted with evidence that disputed his initial statements , '' Tobias said Saturday . Bravo had told investigators he got into `` an altercation with Aguilar '' the night the college student went missing , police said . The suspect then left Aguilar in a parking lot in the central Florida city , prompting police to warn that Aguilar may be disoriented and/or seriously injured . Aguilar 's father told CNN affiliate WCJB that his son disappeared after a fight over a girl . After talking with police a day after his disappearance , Bravo was held for mental examination after threatening to harm or kill himself . He was later charged with depriving a victim of medical care , a third-degree felony , and was in custody at the time he was charged with murder , according to Tobias . Scientists have confirmed lime rock residue was found on Bravo 's vehicle , police said Saturday . `` We believe that Christian Aguilar may be located near areas of lime rock , '' Tobias said . The police spokesman previously said , `` we would ... encourage property owners , residential or business , who may have lime rock roads on their property , that were accessible to the general public , to search those properties for any suspicious areas of ground that appear to have been disturbed , '' Tobias said . `` We are also requesting information from anyone who may have seen a suspicious vehicle , likened to a Blue Chevy Blazer , in any remote areas on the night of Thursday , September 20 . '' Authorities have used helicopters and K-9 units to search for Aguilar , to no avail . His relatives have plastered the area with fliers , taken to Twitter to generate leads and invited a nonprofit search group to help look for him alongside family members and police . Bravo 's lawyer said his family initially volunteered to help in the search , only to be politely turned down by the victim 's relatives . Gov . Rick Scott was to join the search Saturday in a wooded area in Gainesville , his office said . CNN 's Joe Sutton and Greg Botelho contributed to this report .
NEW : Blood found in suspect 's vehicle , police say . NEW : Student 's backpack found at suspect 's home , police say . Christian Aguilar , 18 , was last seen September 20 in Gainesville , Florida . Pedro Bravo , also 18 , is charged with murder .