Ice caused AirAsia QZ8501 flight crash.
Caskets containing the remains of AirAsia QZ8501 passengers recovered from the sea are carried to a military transport plane before being transported to Surabaya, where the flight originated, at the airport in Pangkalan Bun, Central Kalimantan January 2, 2015.Reuters

The Indonesian government officials have called for an investigation on AirAsia, after it was found that its flight QZ8501 flew 'illegally' out of Surabaya to Singapore on 28 December.

The Indonesian Transport Ministry in its investigations found that the AirAsia flight QZ8501 was operating in violation when it flew out of the Surabaya's international airport on 28 December and crashed into the Java sea.

The investigating agencies are now trying to figure out how AirAsia was able to operate the flight on Sunday, when it only had permission to operate on the route on Mondays, Tuesdays, Thursdays and Saturdays.

"So AirAsia has committed a violation of the route that has been given to them," Transport Ministry spokesman J.A. Barata told The Wall Street Journal. The Aviation Ministry following the revelation suspended the AirAsia flight to Singapore on Friday.

The government will be investigating on why AirAsia was flying the route outside its permitted schedule. The aviation ministry also will face the probe as it is strongly believed that the airline operaters were working in nexus with government officials to function illegally.

"Frankly speaking, it's a bit late for us to find out about this," Indonesia's acting director general of aviation, Djoko Murjatmodjo said. "One thing that's certain is the days that they are flying aren't the same as the days they were given. There was no request for changes," Murjatmodjo added.

AirAsia meanwhile has refused to comment on the investigation ordered by the government. The airline operater however stated that it would fully cooperate with the government investigation. 

The development came as Indonesia's search-and-rescue agency said it had discovered four large pieces of the plane on the floor of Java Sea, as the 31st body from was recovered. The AirAsia flight QZ8501 crash killed 162 people, including its crew members.