Four crew members from an Aqua Expeditions cruise ship are still missing after the Aqua Amazon exploded and sank on the Amazon River last Saturday.

According to the luxury adventure cruise line, the 24-passenger ship “suffered a very serious accident…that caused an explosion and resulted in the sinking of the ship.”

There were no passengers onboard the ship but of the 17 crew, four are still missing and several were rushed to the hospital to treat injuries.

“All efforts are being made to get a better understanding of the status of the missing crew.  The entire operations team is on the ground providing logistical support with local emergency services,” said Aqua Expeditions founder and CEO Francesco Galli Zugaro.

The next sailing was scheduled for July 16 but passengers affected have since been reassigned to the Aria Amazon.

This is the second fire-related incident on the Amazon this year. In April, two American tourists died on an International Expeditions ship after a fire broke out in their cabin and the couple were unable to escape.

Also last week, bandits attacked passengers on an Amazon Discovery ship. Six Australians were onboard the ship when the robbers climbed aboard and stole valuables worth over $26,000.