Authorities in Colorado are searching for an Indigenous woman who went missing last week on her first night in Denver after relocating to the city.

Christine Tail, a 32-year-old member of the Oglala Sioux Tribe, was last seen on June 14 in downtown Denver, according to a Missing Indigenous Person Alert issued by the Colorado Bureau of Investigation.

Tail had just moved from South Dakota and went missing during her first night in Denver, according to the alert.

Tail, who has bleached blonde hair with pink tips, was last seen wearing a T-shirt with a pride logo, blue shorts and white sneakers, the alert said.

Tail and her girlfriend, Tanya Lance, moved to Denver to "make a better life," Lance's mother, Carol Red Bird, told CNN. Red Bird said that both Tail and her daughter used to stay with her often when they lived in South Dakota.

The couple were exploring the city's downtown area when Tail wandered off, Red Bird said. Lance told her she spent the night looking for Tail but couldn't find her and called relatives in South Dakota to help her search for Tail.

"Christine just sticks very close to my daughter," Red Bird said, adding that it is unusual for Tail to not be in touch with them for several days. Red Bird said Tail is normally very active on social media but hasn't posted anything in several days.

Tail's girlfriend and her family from South Dakota, along with members of the grassroots group Missing & Murdered Indigenous Relatives Taskforce of Colorado, have been putting up flyers with Tail's photo and searching the downtown area.

Law enforcement officials issued a Missing Indigenous Person Alert on Sunday, four days after Tail was last seen and three days after a relative first left a message with police. The alert system was launched late last year, and it is designed to be activated when an Indigenous person is reported missing to law enforcement.

The Denver Police Department said in a statement to CNN that a family member called police again on Saturday morning and an officer was dispatched to take a report, but the missing person alert was not issued until Sunday.

Indigenous advocates and Tail's friends are concerned the delay in issuing the alert could have a negative impact on finding Tail.

"This is literally a life-or-death situation, especially when it's some of our young relatives that go missing," said Monycka Snowbird, an Anishinaabe activist and member of the Colorado task force. "They are at such high risk of trafficking situations that it's terrifying to think where Christine might be."

The legislation creating the alert system requires law enforcement agencies that receive a report of a missing Indigenous person to notify the CBI within eight hours of a report of a missing adult or within two hours of a report of a missing child.

The Denver Police Department said a family member left a voicemail for its missing and exploited person unit on June 15 that said she wanted to make a missing person report, but provided no details. The following day, only one detective was on duty and could not call them back immediately due to a large caseload, police said in a statement to CNN.

They said the MEP hotline directs callers to the department's non-emergency number or 911 if they need assistance, and they said the message would be updated for clarity.

In their statement, Denver Police said there was an "internal misunderstanding" about whether the CBI had started the process to issue the alert and says it is reviewing its procedures.

"The MEP Unit will review the chronology and steps taken with this report to ensure reports are taken and alerts are issued in a timely manner and in accordance with state law," the police department said.