The circumstances surrounding the player's death are not yet known and Warriors managing director Jim Doyle said the club contacted Mailei's family after learning of the news.
"It's a sad time when any young life is lost and losing a young member of the club has been a great shock," Doyle said.
"It's a dreadful time for Tala's family and also for all of us at the club.
"We're giving the family all the support we can and will also be offering the same for all our players and staff."
Many took to social media to pay tribute to the young league star:
"You will be sadly missed by members of my whanau who knew you as a very talented young man and friend and their brother," wrote Sonny Wiparata.
"Gone too soon little brother," wrote another.
Less than a month ago, Mailei shared a post on Facebook reading: "Goals re looked at. New goals added. Motivated to do something that has never been done before. Ain't no use listening to people who don't believe and see what you see. Stepping outta your comfort zone ain't easy, but its a day to day decision that needs to keep being made."
The 17-year-old represented Christchurch's Aranui High School at the national secondary schools tournament at Papakura in early September and returned to Auckland the following month for the Warriors' annual open trial for the National Youth Competition under-20 team.
The promising centre impressed Warriors coaches and was invited to train with the club in January.
"He played in the schoolboys and our scouts thought it was clear he had a bit of talent," Doyle said.
"He came up with a bunch of other kids to play in the trial and played well and we invited him to come back. He was on the fringes of the wider squad and was due to come back and train next year after being home for the Christmas break."
Yesterday, his former school paid tribute to the player on Facebook:
"The community of Aranui High School is deeply saddened by the sudden passing away of a rising star in the rugby league world, Tala Mailei, who spent 2015 in the Aranui League Academy, under the guidance and direction of Te Wairau. Our deepest condolences go to his aiga [family], friends, fellow league players and to the Warriors. RIP Tala."