ABC7 has learned a former friend of the nursing student, Giselle Estaban, is considered to be a person of interest in this case. The former friend went to high school with Le in San Diego and, at one point, they even had the same boyfriend.
Union City apartment complex residents say police swarmed Estaban's home. One resident described what bothered her and said, "Just hearing the police and foot activity in and out all through the night, through the weekend actually."
Another resident who didn't want to be identified on camera said, "We fear for our safety. There were a lot of police, especially when the crime lab came by and they're knocking on every door until Sunday morning. We noticed there was a lot of activity in the garage. They were doing fingerprinting on her car and searching her apartment."
They say officers searched Estaban's car, her apartment, and even her trash while a crime lab van stood by for eight hours Sunday. Police say Estaban was eventually released, but resident say she never returned to the apartment complex. Why focus on her?
"We know she's a former friend of Michelle's. I know that... they've been disgruntled with each other in the past," said Lt. Roger Keener with the Hayward Police Department.
Esteban claims Le dated her boyfriend and that ruined her relationship with the man who also fathered her 5-year-old child.
"Currently, she's the only one we felt we had enough to pursue further," said Keener. "It doesn't mean that more aren't going to come to light."
On Saturday, police investigators brought Estaban to the station after searching her home. Police confiscated her cell phone and computer after executing a search warrant.
"We explained to her the circumstances that we're investigating and ultimately, after speaking to her, we released her," said Keener.
Estaban told ABC7 she is innocent of anything that's related to Le's disappearance. No charges have been filed against her, but police are still considering her to be a person of interest.
Le disappeared Friday evening from the Kaiser hospital where she was attending a nurse's mentoring meeting. Le told a colleague she was going to her car, parked in the hospital's garage, to get some things. Le never returned from her break. Her white Honda was found later on a street not far from the hospital. Police say the car was found locked as if whoever was the last to operate it wanted to protect the belongings inside.
On Monday, Le's family and friends passed out fliers outside Kaiser Hospital in Hayward where she worked, hoping to generate some leads. Le's father flew in from Vietnam Friday evening and the family is offering a $20,000 reward for information.
"We met with the family last night and gave them the progress on the case," said Keener.
Police say they are looking at everything, including security cameras located inside the parking garage of the hospital. The pressing question on their minds: Did Le drive her car out of the garage, or was it someone else, and did another car follow her as she left?
"As time goes by, clearly there becomes a greater and greater concern for Michelle's safety," said Keener.
Police are also tracing calls made with Le's cellphone. They say that the last calls from that phone were made around noon on Saturday.
Le's family plans on holding a community vigil on Friday.