Two boats collided over the weekend on the Congo River, killing at least 30 people and leaving dozens missing, local authorities in Congo said Monday.

The motorized wooden boats crashed into one another on Sunday evening near the Ngombe-Lukolela area in the province of Equateur, according to the provincial interior minister, Crispin Mputu.

The reason for the crash was not immediately clear. Mputu said nighttime boat navigation has led to many accidents in the past. The minister told The Associated Press that the 30 killed in the crash have already been buried.

One boat was traveling from Ubangi, in the northwest, to the capital of Kinshasa, and the other from Kinshasa to Lukolela, close to where the collision happened, Mputu said, and added that search efforts continue to find more victims and survivors.

A member of the security forces who said he witnessed the crash from the riverbank told the AP that the “returning from Ubangi was overloaded with goods and collided with the one coming from Kinshasa.”

“Almost all the passengers on board were trapped underwater, and the boat itself also sank,” he added, speaking on condition of anonymity, because he was not authorized to speak publicly without permission from his superiors.

Deadly boating tragedies are common in the central African country, where late-night travel and overcrowded vessels are often blamed. Poor safety standards and lack of infrastructure in remote parts of the country also contribute to the hundreds killed in boat disasters in recent years.

In July, a wooden boat transporting students back from state exams sank in central , killing at least 20 people.

The vessel was traveling in Kasai province when it sank while entering the confluence of the Sankuru and Kasai rivers.