Rescue efforts are racing against time as the floating bodies they are trying to retrieve from the downed AirAsia Flight 8501 are starting to sink. Officials said that bodies typically sink after 10 to 14 days of floating in the sea, and the search-and-rescue efforts have entered their 10th day.

Two more bodies were recovered on Tuesday, bringing the total recovered body count to 39, reports Channel News Asia. Roughly 162 people were on board the flight when it left Surabaya, Indonesia, for Singapore on Dec. 28. Medical experts have said that the remaining bodies that have managed to float are expected to sink soon.

All of the bodies found so far were spotted floating, with some still strapped into their seats. So far, 13 of the recovered bodies have been identified, with the rest having been exposed to the elements for too long.

Rescue officials said that the search has been hampered by choppy weather, with waves as high as 10 feet preventing sonar equipment from locating the plane’s emergency beacons or divers from going underwater to retrieve bodies. “The black boxes could still be inside the [fuselage] of the plane,” said Suyadi Bambang Supriyadi, director of operations at the search-and-rescue agency, according to the Wall Street Journal. “They could be surrounded by aluminum metal, and with the aircraft possibly covered with silt, the signal may not be strong.”

The batteries on the beacon are expected to last for only 30 days. Since the incident, Indonesian authorities have called for aviation officers to be held accountable for permitting the supposedly unauthorized AirAsia flight to take off, with four air traffic control officers removed from their posts. The Transport Ministry has also called for a review of the safety protocol and procedures of all domestic airlines, requiring pilots to attend mandatory briefings with airlines’ officers before a flight.