Two women and two men died when rafts collided on the Thunder River Rapids ride at the Dreamworld tourist attraction on the Gold Coast.

Dreamworld owner Ardent Leisure said in a statement Tuesday that prosecutors had filed three charges under Queensland state workplace health and safety laws over the disaster.

Each charge carries a maximum penalty of A$1.5 million, making a total potential penalty of A$4.5 million.

The company, which came in for heavy criticism for the way it handled the tragedy, including trying to reopen before the funerals had taken place, said there had been “considerable change” at the theme park in the past few years.

“Dreamworld has taken substantive and proactive steps to improve safety across the entire park and continues to enhance existing systems and practises, as well as adopt new ones,” it said in the statement to the Australian Securities Exchange (ASX).

Ardent has previously said it lost millions of dollars after the tragedy and has pledged to build a memorial to the victims.