According to state media, the sinkhole opened up at 2:30 p.m. local time Sunday in Dazhou, Sichuan province.
Two victims died after being taken from the pit and rushed to hospital, state media said. They were reportedly married only days before.
Efforts to Rescue the other victims, a father and his son, were unsuccessful, with the two found dead on Tuesday afternoon.
Rescuers believed the final two were trapped around 10 meters (32 feet) underground, some two meters further than local rescuers' equipment could reach.
"Gao Mingyue, a fire service official, told CCTV, earlier in the search."
"We have to move excavators to a lower
More than 40 firefighters were involved in the rescue effort.
Sinkholes typically forms when acidic rainwater dissolves limestone or similar rock beneath the soil, leaving a large void that collapses when it's no longer acceptable to support the weight of what's above – whether it's an open field, a road or a house.
The cave-in area is over 10 square meters (107 sq ft), the broadcaster said.
"When we arrived, the caved-in area was not big, but only two meters in length and depth." "Firefighters at once evacuated while doing the rescue work, "Gao said.
The presence of high-voltage power cables and water pipes made the rescue work especially difficult.
"Given what we found in the hole, cables are crossed in a mess, including two high-tension lines, weak electric wires and gas pipelines," Gao added.