At least one person is missing and nearly 50,000 people have been evacuated after the sluice gates of a dam in central Myanmar burst, flooding around 100 villages on Wednesday morning.

State media reported that the Swar Chaung dam in Yedashe township, Bago region, began to overflow on Monday but told residents there was no cause for concern. At around 5:30am on Wednesday, however, a deluge of water burst out of the dam, inundating acres of rice fields and causing a bridge on a highway connecting Yangon and Mandalay, Myanmar’s biggest cities, to buckle.

“The damage is not bad, but the bridge is unusable because the water is still receding,” said Aung Zaw Htay, an official from the Myanmar Fire Services Department.Authorities have not yet released any casualty figures.

The Swar Chaung dam was built around 2001, according to Kyaw Myint Hlaing, the director-general of Myanmar’s irrigation department. He said the cause of the breach had not yet been identified, but he ruled out a flaw in the dam’s design.

“The design of the dam’s spillway is like the beak of a duck. One of the ‘beaks’ broke, but the dam itself has not broken. This is related to the monsoon, but also related to unknown factors,” he said.

“We are trying our best to find a temporary solution to stop the remaining water behind the dam from overflowing,” he said.

The breach occurred after a series of earlier floods in southern and central Myanmar in late July, during which the authorities only instructed many residents to evacuate after their homes were already under several feet of water.

About 150,000 people were displaced, many of whom have become reliant on private food donations after their crops were destroyed. Residents of one flooded village in Bago region said authorities had only provided aid to pregnant women and mothers of children under six months old.

A hydroelectric dam in southern Laos collapsed in July, killing at least 27 people and displacing thousands. When asked if the Swar Chaung failure resembled the Laos disaster, Kyaw Myint said: “I’m not familiar with the dam in Laos.”

Officials said the plains below the dam were still flooded on Wednesday evening, but that the water covering the highway was slowly receding. Aung Zaw Htay, the fire department official, said his team’s priority was to clear the area in order to return the roads to working condition.

As in earlier floods, Myanmar authorities have placed much of the responsibility to avoid danger on the victims. The fire department officialsaid that by the time his team arrived“the residents were already evacuating themselves”.

“The villagers have had experiences dealing with it, so there wasn’t much trouble. The villagers who live around here know about the possibility of flooding,” he said.