WUZHOU, China >> Hundreds of people in rain gear and rubber boots searched muddy, forested hills in southern China on Thursday for the second flight recorder from a jetliner that crashed with 132 people aboard.

No survivors have been found since the China Eastern Airlines Boeing 737-800 dived into a mountainous area Monday, but authorities say they still are looking.

Some human remains and engine parts were found, as well as items from the cockpit and some belongings to passengers, officials said. State TV showed searchers on a denuded slope trying to dislodge a white wing section with the airline’s red-and-blue logo.

One of two black box recorders, believed to be the cockpit voice recorder, was found Wednesday. Its outer casing was damaged but the orange cylinder was relatively intact, investigators said.

The U.S. National Transportation Safety Board said talks were ongoing with China over dispatching an expert to participate in the investigation, as is standard when the planes involved are from American manufacturers.

“Travel to China is currently limited by visa and COVID quarantine requirements. We are working with the Department of State to address those issues with the Chinese government before any travel will be determined,” NTSB spokesperson Peter Knudson said in a statement.

China Eastern, one of China’s four major airlines, said Thursday the Shanghai-based carrier and its subsidiaries have grounded a total of 223 Boeing 737-800 aircraft while they investigate possible safety hazards.

China Eastern earlier said the grounding of planes was a precaution, not a sign there was anything wrong. The airline has said the plane that crashed was in good condition and its flight crew was experienced and in good health.

The plane that crashed was flying from Kunming, the capital of Yunnan province in China’s mountainous southwest, to Guangzhou, a major city and export manufacturing hub in the southeast. Authorities say there were no foreign passengers aboard.

Investigators have said it is too early to discuss possible causes. An air traffic controller tried to contact the pilots several times after seeing the plane’s altitude drop sharply but got no reply, officials have said.

The government has yet to release the pilots’ names, but news reports identified the captain as Yang Hongda. The co-pilot, according to news reports, was Zhang Zheng, a veteran with 32,000 hours of flying time in a 30-year career.

An unidentified former colleague of Zhang cited by the online news outlet The Paper said he was a mentor to young pilots who had a “sunny disposition” and captained the air academy’s basketball team.

A second co-pilot, Ni Gongtao, was flying with them to gain experience, according to news reports.

On Thursday, pumps were being used to drain a pit at the center of the crash site as light rain hampered work for a second day.

“The rainstorm made the job harder,” said Zheng Xi, fire chief of the Guangxi region, at a news conference. Zheng said muddy roads were so hard to get through that some searchers walked to the site carrying tools and other equipment.

More than 300 searchers were taking part, said Huang Shangwu, a deputy fire chief.

“The water pumping yesterday greatly contributed to the finding of the black box,” Huang told reporters at a command center near the crash site.

The Boeing 737-800 was cruising at 29,000 feet (8,800 meters) when it crashed, starting a fire that could be seen in NASA satellite images.

The government has sealed off a large area around the crash site and tried to control information about the disaster.

Foreign media were escorted into the zone for the first time Thursday. Police and other vehicles were parked along the highway. Journalists were driven down small roads covered in red-brown mud to the command center.

When they passed a woman in tears who was being led away, security officials used open umbrellas to try to block the journalists from filming from their vehicles.

Searchers have been using hand tools, metal detectors, drones and sniffer dogs to comb the heavily forested and steep slopes. Wallets, identity and bank cards and human remains have been found.

The “black boxes,” usually painted orange so they can be easily found, are considered key to figuring out what caused the crash.

Cockpit voice recorders can capture voices, audio alerts and background sounds from the engine or switches being moved. The flight data recorder stores information about speed, altitude and direction, as well as pilot actions and performance of important systems.