"I'm never going to have her back to see her again, to tell her I'm sorry or that I love her," said Sandra Anaya.
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In the summer of 2005 Anaya's daughter Alexandra went missing from her home during the night. Three days later her torso was found in the Little Calumet River.
Thursday, the FBI doubled the reward for information in the case to $20,000.
READ MORE: Sweet potato, DNA links suspect to 12-year-old murder, prosecutors say
"I'm sure some people were scared, but time has passed. Maybe this will encourage them to come forward even more now," Anaya said.
"It's a devastating situation for any parents to face, and to not have resolution for 18 years, it's unacceptable," said FBI Special Agent Siobhan Johnson.
Johnson said information can be given anonymously.
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"It's been an entire lifetime. This can be the moment that someone can give a tip to change the family's lives," she said.
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Alex Anaya was in the seventh grade when she was killed. She loved volleyball and soccer, and wanted to be a veterinarian.
"She always lit up the room, she was the type who didn't just give you a wave, she gave you a hug and a kiss," her mother said. "Just tell us what happened. I want to know what happened."
While her mother will always live with the pain of losing her child, Anaya hopes there can be more room for peace for herself and her family if someone is brought to justice.
To report tips, even anonymously, the public can call 1-800-CALL-FBI or visit tips.fbi.gov.