The third day of searching for victims and wreckage of a B-737-500 crash in the sea off Jakarta was focused Monday on an area where the "black box" flight recorders were located the previous day.

Searching around the clock, about 2,600 rescuers with 13 planes and 53 ships have been deployed, recovering human remains believed to be those of some of the 62 people who were on board Sriwijaya Air Flight SJ182 as well as suspected debris from the aircraft.

A rescue team is pictured in the search operation for the Sriwijaya Air Flight SJ182 plane on Jan. 10, 2021 in Jakarta, Indonesia. (Getty/Kyodo)

"The search is focusing on an area narrower than before but it can be expanded, depending on the sea currents and waves that may cause pieces of the plane's parts and human remains to drift further," the National Search and Rescue Agency's operational director Brig. Gen. Rasman, who like many Indonesians goes by a single name, told reporters.

So far, no survivors have been found.

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The plane disappeared from radar minutes after taking off from Jakarta's Soekarno-Hatta International Airport on Saturday afternoon and is thought to have crashed between the islands of Laki and Lancang just north of the capital.

On Sunday, the black box flight recorders were located in the vicinity of the suspected crash site, but they had yet to be recovered. Among debris found Sunday was an aircraft turbine.

The departure of the plane, which was bound for the West Kalimantan provincial capital Pontianak, was delayed by heavy rain.

It took off from Jakarta's main airport at 2:36 p.m and a minute later requested to ascend to 29,000 feet (8,839 meters).

However, at 2:40 p.m., air traffic control inquired with the pilot as to why the plane was heading northwest instead of its expected path. A few seconds later, it disappeared from radar.

Flight tracking website Flightradar24 showed that after taking off, the plane climbed to 10,900 feet in approximately four minutes, but then went into a steep descent over the next 21 seconds, with the last received data placing it at 250 feet from the water's surface.

The cause of the crash remains unknown. Local fishermen told television networks there was heavy rain at the time of the incident and they saw a plane plunge into the sea. They also reported hearing two explosions.The U.S. National Transportation Safety Board will be involved in the investigation as the plane was made in the United States, while the Transport Safety Investigation Bureau of Singapore has also offered to assist.

Among the 62 people aboard the plane were 10 children, including three infants, and 12 crew members. All were Indonesians.

Established in 2003, Sriwijaya Air is the country's third-largest airline and is regarded as having a good safety record. Before Saturday's crash, it had been involved in five minor incidents, none resulting in casualties.

The crash was the second involving a B-737 aircraft in Indonesia in recent years. In October 2018, a B-737 MAX 8 operated by low-cost carrier Lion Air crashed off the northeast coast of Jakarta immediately after takeoff, killing all 189 passengers and crew.

The Lion Air incident, along with another involving an Ethiopian Airlines aircraft in 2019, caused the grounding of B-737 MAX airliners. The B-737-500 model involved in Saturday's crash was an earlier generation not affected by the grounding.