Police say Maria Gonzalez was killed while her dad was at work. Now, her father said he won't rest until her killer is caught.

PASADENA, Texas (KTRK) -- An 11-year-old girl is dead after police said she was found strangled to death under a bed in her Pasadena home on Saturday.

The Pasadena Police Department said at about 3:07 p.m., it responded to an apartment complex at 1004 Main St. with a caller saying his 11-year-old daughter was not breathing.

When paramedics arrived, they pronounced the girl dead. She was later identified as 11-year-old Maria Gonzalez by authorities.

During the investigation, it was discovered that Maria had been found under a bed by her father, Carmelo Gonzalez, after returning home from work, according to police.

Her father left for work at about 10 a.m. and had been in communication with Maria over the phone, police said.

Shortly after Gonzalez left, police said he received a message from Maria stating someone was knocking at the front door.

In an evening press conference on Tuesday, Pasadena Police Chief Josh Bruegger said the father called family members who live at the same apartment complex to check on Maria.

After a brief search, police said the family was not able to find her.

Maria's cause of death was ruled as asphyxiation due to strangulation and blunt force head and neck trauma, according to the medical examiner. Additional investigation determined that she had also been sexually assaulted.

Police said there was no forced entry into the home and do not have any suspects.

"At this point, the father's alibi checks out, so he is, at this point, not considered a suspect in this investigation," Bruegger said, adding the father and daughter have been living at the apartment for three months. The mother currently lives in Guatemala.

According to Bruegger, they've taken DNA samples from some people in the complex, but getting cooperation has been a challenge.

"Whoever saw something just after 10 a.m. on Saturday at that particular apartment, we're asking them to come forward with the information they might have," Bruegger said.

Anyone with information on the homicide case is asked to contact Detective M. Quintanilla at 713-475-7803 or Detective S. Mata at 713-475-7878.