Rescuers conduct search and rescue work at a plane crash site in Tengxian County, south China's Guangxi Zhuang Autonomous Region, March 24, 2022. (Xinhua/Lu Boan)

Pieces of engine wreckage from the passenger plane that crashed in south China's Guangxi earlier this week have been found, an official told a press briefing on Thursday.

The main impact point of the plane crash has been basically determined, said Zhu Tao, head of the aviation safety office of the Civil Aviation Administration of China.

Most of the plane wreckage was scattered within a radius of about 30 meters of the main impact point and the depth from the surface extends to about 20 meters underground, Zhu said.

A suspected wreckage piece, 1.3 meters long and 10 cm at its widest, was also found in farmland around 10 km away from the crash site, said Zheng Xi, head of the fire brigade of the Guangxi Zhuang Autonomous Region.

As of 4 p.m. Thursday, a total of 183 pieces of aircraft wreckage, some remains of victims and 21 pieces of belongings of victims have been found and handed over to the investigation team, Zheng said.

Rescuers expanded the search area on Thursday despite persistent rain that has complicated rescue efforts over the past days, Zheng said.

Rescuers conduct search and rescue work at a plane crash site in Tengxian County, south China's Guangxi Zhuang Autonomous Region, March 24, 2022. (CAAC News/Handout via Xinhua)

Rain caused waterlogging at the core crash site and increased the risk of small-scale landslides. Large rescue vehicles and equipment was not able to reach the area due to the narrow and slippery mountain road, he said.

The area east of the core crash site is mainly virgin mountain forest and the steep and heavily-wooded terrain increased the difficulty of the search-and-rescue effort, Zheng said.

"We will work to shorten the search-and-rescue time and improve the efficiency of search and rescue as much as possible, with enough being done to ensure the safety of our rescue staff," he said.

The Boeing 737-800 plane with 132 aboard crashed Monday in a village in Tengxian County in the city of Wuzhou. No survivors have been found so far. One black box from the plane has been recovered.

The recovered black box was sent to a decoding laboratory in Beijing on Wednesday night, and the data downloading and analysis work is underway, Zhu told reporters.

One of the two black boxes of the crashed plane is recovered in Tengxian County, south China's Guangxi Zhuang Autonomous Region, March 23, 2022. (Photo by Xu Dong/Xinhua)

The possibility that the data storage unit of the cockpit voice recorder was damaged cannot be ruled out at present, Zhu said, adding that the rescuers are going all out to locate the second black box, or the flight-data recorder.

Following the crash, China Eastern Airlines and its subsidiaries temporarily grounded 223 Boeing 737-800 aircraft, and the airline has launched a sweeping safety overhaul, Liu Xiaodong, head of the airline's publicity department, told the press briefing.

All grounded aircraft are undergoing checks and maintenance according to the highest safety standards to ensure that they meet the airworthiness requirements, Liu said.

Liu added that 305 family members of 56 passengers aboard the crashed plane had arrived in the city of Wuzhou by Thursday morning, with over 200 family members having been to the crash site.