(CNN) -- The mother of a missing 7-year-old Oregon boy pleaded for her son's safe return Tuesday, imploring him to "never give up hope."
"Our goals are to expand the search for Kyron and to bring him home as quickly as possible," said Desiree Young, the mother of missing Kyron Horman, who was last seen June 4.
Young, standing alongside Kyron's father, Kaine Horman, gave the statement during a press conference intended to provide an update on the investigation.
However, few details were given by Multnomah County Sheriff's Office authorities, who declined to elaborate on what they called "significant progress" in the case.
"Authorities remain determined to reach a successful solution," Capt. Monte Reiser said.
"We believe that Kyron's disappearance involved criminal behavior because his parents have been deprived of their son for 53 days," he added.
Young expressed confidence in the investigation saying it "continues to be on track and is progressing toward finding Kyron."
She concluded her statement by speaking directly to her son.
"We love you Kyron," she said, her voice breaking with emotion. "Never give up hope. We are all coming to get you to bring you home."
Neither authorities nor Young took questions from reporters.
Meanwhile, Multnomah County Chief Deputy Tim Moore announced that a $25,000 reward for information leading to Kyron has been increased to $50,000, courtesy of an anonymous donor.
Police have not named a suspect in the case, but intense scrutiny has been placed on Kyron's stepmother, Terri Horman.
Terri Horman told investigators that she last saw Kyron the morning of June 4 as he walked down the hall toward his second-grade classroom at Skyline Elementary School.
On Monday, a woman who has been in close contact with Terri Horman was subpoenaed to meet with the grand jury investigating the disappearance.
DeDe Spicher is a friend of Terri Horman's who stayed with her after Kaine Horman filed for divorce shortly after his son's disappearance and moved out of the family home.
In divorce filings, Kaine Horman has said he believes that Terri Horman "is involved in the disappearance of my son Kyron."
Court documents also allege that Terri Horman hired a man to kill her husband.
Spicher appeared before an investigative grand jury in Portland on Monday, according to her attorney, Chad Stavley.
Stavley, who told HLN that he was retained Friday, said Spicher was not asked any questions by the prosecutor but was ordered to return at a future date.
A statement released Friday by Kaine Horman and Young described Spicher as someone who "has been in close communication with Terri [and] has been providing Terri with support and advice that is not in the best interests of our son."
The statement also described Spicher as uncooperative in the investigation and "going as far as to suggest to others that may have information regarding Kyron's disappearance not to cooperate as well."
Stavley disputed those comments Monday, saying Spicher has been "extremely cooperative" with police as they executed search warrants on her home and car. He said she also met with the lead investigator in the case last week for more than three hours.
He added that Spicher is not speaking to Terri Horman.
The Oregonian reported that detectives have asked Spicher about her whereabouts June 4.
According to the newspaper, Spicher was doing gardening work for a Portland homeowner when she "abruptly left about 11:30 a.m."
The homeowner tried reaching Spicher on her cell phone, the newspaper reported, but got no answer. Spicher returned to the house about 90 minutes later, the newspaper reported, citing detectives.
Stavley declined to comment Monday on what Spicher was doing during those 90 minutes.
HLN's Natisha Lance and CNN's Gabriel Falcon contributed to this report.