The boat was travelling from Ngondo, an area approximately 74 miles (120 kilometers) from the province’s capital, Mbandaka, and crashed Saturday night in Bolomba village, Didon Ifete, the administrator for the territory, said on state radio.
Some 200 passengers were rescued and an unknown number of others were missing, he said.
This is the second boat wreck on the Congo River in Equateur province within a week. On October 14, another boat capsized, killing at least 47 people and leaving more than 70 missing.
In January, at least 145 passengers went missing after a motorized boat overloaded with goods and animals sank on the river in northwestern Congo.
Boating mishaps are common on the Congo river and on the nation’s lakes because of the prevalent use of makeshift boats that are often overloaded. The majority of the population in the country’s northwest use the rivers to travel because of a lack of sound roads and because it is a less expensive.
The Congolese government banned night-time river travel throughout the country to prevent accidents, although many defy the directive. Some of the 189 people rescued after a boat capsized in the Democratic Republic of Congo have told the BBC how they managed to survive.
"All my body was under the water, except my head. I clung to a wooden part of the boat until some people arrived with a canoe to save me," said Korami Mopole.
More than 40 bodies have been recovered so far, while rescue workers are searching for 167 people still missing.The boat was reportedly overloaded.
There were more than 300 passengers and cargo on board as it travelled along the River Congo, said a civil society group involved in rescue and recovery efforts.
Another survivor of Friday's tragedy, Michael Busakasa, told the BBC that shortly after the boat left the port in the city of Mbandaka on Friday evening, the crew noticed that the weight was unevenly distributed.
They started moving cement bags to try and balance it. But this did not work. Then a canoe that the boat was carrying was removed and "immediately the boat started to sink", he said.
Mr Busakasa, his mother and sister were taking their father back home after he had been in hospital.
"I don't know how to swim, but my father, my mother and myself were all at the front, at the entrance - that part was still floating and that's what saved us with the help from people who came to our rescue."
Boats are a common mode of transport in DR Congo because of the lack of roads.
However, boat accidents are frequent because of overloading, a lack of maintenance and travelling at night.Many passengers also do not wear life jackets.
Officials say that the boat was sailing at night in breach of safety regulations.
Prominent DR Congo opposition leader and presidential candidate in December's election, Moïse Katumbi, said he was saddened by "this tragedy".
He said it was a "direct consequence" of the government "which tolerates the overnight navigation of dilapidated and overloaded boats".
UN-linked Radio Okapi reports that the provincial government of Equateur, where the accident happened, said it would provide psychological support for children who were injured in the accident and lost their parents.
The radio station said that more than 40 bodies had been so far recovered but the local civil society organisation, Conscious Generation, said that the number was 50.
A survivor told Radio Okapi that the boat, which had left the city of Mbandaka for the Bolomba area in the north-western Equateur province, stalled and lost balance because of overcrowding.
While the crew attempted to rebalance the boat, it overturned with the passengers and cargo before sinking, the survivor added.
On Sunday, the vice-governor of Equateur province provided body bags and coffins for the burials of some of the victims.