SAN ANTONIO -- After evidence technicians found stains and spatter at the home of missing girl Rosa Sandoval, 12, lab tests will determine if it is blood, body fluids or a household substance.

Sandoval disappeared four weeks ago and hasn't been seen since.

Police said evidence technicians found what appears to be blood stains and bloodied handprints on the walls of her room, which she shares with 17-year-old sister Gabby.

"We used a chemical called luminol, which will react not just on blood, but other body fluids in a particular place," said Sgt. Gabe Trevino of the San Antonio Police Department.

Traces were also found in an adjacent bedroom belonging to her brother.

Questions were raised about how the chemical test was administered, but the San Antonio Police Department said proper procedures were followed.

Meantime, an employee with Steam King showed up at the home Friday to clean up residue left behind from the police search last Friday.

It could take several weeks before tests are completed on portions of the walls and on a mattress taken from the home.

It could take several weeks before tests are completed on portions of the walls and on a mattress taken from the home.