(CNN) Lionel Messi has urged those tasked with overseeing the search for missing soccer star and fellow Argentinian Emiliano Sala not to give up while there is still hope.

In an emotional post on his Instagram story , the Bacelona star offered his support to Sala's family while urging authorities to keep on looking after the search was abandoned Thursday.

"As long as there's a chance, a thread of hope, we ask that you please #DontStopLooking for Emiliano. All of my strength and support to his family and friends. #PrayForSala," he wrote Friday.

Messi's post comes the day after Sala's sister, Romina, pleaded with authorities to restart their search for the soccer player after it was abandoned Thursday.

The three-day search was called off after police conceded that any hopes of finding the 28-year-old alive were "extremely remote."

Sala, who had just signed for Cardiff City, was flying from Nantes to the Welsh capital after saying farewell to his former teammates following his $19.3 million move to the Premier League club.

Rescue workers had been attempting to locate the plane since it disappeared from radar near the Channel Islands just before 8:30 p.m. local time (3:30 p.m. ET) Monday. The plane had requested descent on passing Guernsey but disappeared from radar at about 2,300 feet.

But police finally called off the search at 15.15pm local time (10.15 a.m ET) Thursday, adding they had been unable to find any trace of the plane, pilot David Ibbotson or Sala.

Supporters gather to pay tribute to Argentinian soccer player Emiliano Sala, in Nantes.

"Please, please, please don't stop the search. We understand the effort but please don't stop the search," Sala's sister Romina urged during an emotional news conference in Cardiff Thursday.

"For us, they are still alive. It is difficult to express our feelings at the moment because everything is really hard.

"Emiliano is a fighter. I'm asking you please, don't stop looking for them. It's been three days and I've still got hope that they're alive.

"It's terrible, it's desperate not knowing anything. We don't have certainty of anything."

FC Nantes has learnt that the search for the missing plane was called off.



This search mustn't stop, @GuernseyPolice



The club and its supporters strongly ask for the search to find @EmilianoSala1 to go on, for his family and his near relatives. Together for Emi ! #PrayForSala pic.twitter.com/7C1PrMUV7R — FC Nantes (@FCNantes) January 24, 2019

Romina Sala's words were also echoed by Nantes with the club urging those responsible for the rescue mission to reconsider.

"FC Nantes has learnt that the search for the missing plane was called off. This search mustn't stop, @GuernseyPolice," the club tweeted.

"The club and its supporters strongly ask for the search to find @EmilianoSala1 to go on, for his family and his near relatives. Together for Emi!"

A tribute to Sala was held in Nantes on Thursday afternoon with the club inviting 300 members of the public to a training session.

A portrait of the player has been placed in a street in the city, and would also soon be placed outside the stadium, to give well-wishers an opportunity to place flowers, candles and messages of support near it.

#FCNantes Après Valentin Rongier, coach Vahid a pris la parole... «Plus que jamais on doit rester unis...», a-t-il dit aux supporters. #Sala pic.twitter.com/kOJ0FrSubM — David Phelippeau (@dphelippeau) January 24, 2019

After training, the Nantes captain Valentin Rongier addressed supporters, urging them to keep hold to the belief that Sala may yet still be alive.

"We ask you to stand united with us," Rongier said. "We ask you to respect the family who absolutely refuse to talk about mourning and ask us to keep believing.

"It is for this reason that we are not going to have a minute's silence or a minute's applause because we still have hope."

Cardiff City fans unveil a flag in front of tributes for their forward Emiliano Sala after the search for the missing footballer and pilot was called off.

In Cardiff, the news to call off the search was met with shock.

"We were looking forward to providing Emiliano with the next step in his life and career.

"Those who met Emiliano described a good-natured and humble young man who was eager to impress in the Premier League.

"The response from the football community has been truly touching and we place on record our sincere thanks to those who have sent messages of support.

"We also thank everyone involved with the search and rescue operation, and continue to pray for Emiliano, David Ibbotson and their families."

Emiliano Sala scored 12 goals for Nantes this season before securing a move to the Premier League.

Sala had been expected in Cardiff for his first day of training on Tuesday and would probably have made his Premier League debut at Arsenal on January 29.

But his failure to arrive in the Welsh capital sparked a rescue mission over the English Channel after the plane, a single turbine Piper Malibu, disappeared from radar after departing from Nantes.

On Wednesday it emerged that Sala sent a WhatsApp audio message to a group of friends while on board the plane.

It was unclear exactly when Sala sent the message but he describes being tired and can be heard yawning. Sala appears to joke about the aircraft, telling his friends in a deadpan tone: "I'm here on the plane and it looks like it's going to fall down in pieces." He then says that training with Cardiff would start the next day.

Near the end of the recording, he appears to make another joke, saying: "If in an hour and a half you don't have news from me ... I don't know if they would send someone to look for me because they won't find me, but you will know. Dude, I'm so scared."

Throughout the message, his voice is monotone and there is no indication that his comments about the state of the plane are anything but dark humor. Sala's family spokesperson confirmed to reporters in Argentina that the message was genuine and expressed dismay that it had been made public.

Nantes football club supporters gather after it was announced that the plane Argentinian forward Emiliano Sala was flying on vanished.

The UK Air Accident Investigation Branch (AAIB) has opened an investigation into the plane's disappearance.

"We are looking at all operational aspects of the flight including licensing," an AAIB spokesman told the UK Press Association.

Rescue teams searched 1,700 square miles and scanned through phone data and satellite imagery but were unable to find any trace of the plane.