ESTREITO, Brazil (Reuters) – Brazilian state and federal authorities assessed on Tuesday the risks of water contamination after trucks carrying sulfuric acid and agricultural pesticides fell into a river on Sunday in a fatal bridge collapse.

The center span of a 533-meter (583-yard) bridge connecting the towns of Estreito in Maranhao state and Aguiarnopolis in Tocantins state disappeared as vehicles crossed over the Tocantins River on Sunday in the afternoon.

The Maranhao state government and the Tocantins fire department confirmed three more deaths in separate statements Tuesday, raising the death toll to four, and with more than 10 people still missing.

Rescue divers called off their efforts on Sunday after it was seen that trucks carrying sulfuric acid had fallen into the river.

“We are waiting for specific institutions to collect and analyze the water so that we, together with 25 divers, can dive to get the victims who are in the bed of the Tocantins River,” said Maranhao fire brigade Colonel Magnum Coelho.

According to the Brazilian water regulator ANA, three trucks carrying a total of 76 metric tons of sulfuric acid and about 25,000 liters of agricultural pesticides fell into the river.

In a statement on Monday night, the agency said it was monitoring the risk of contamination with the secretary of the environment in Maranhao, and said water samples would be collected from the Tocantins River.

It was not immediately clear if the chemicals had leaked, and if so how much.

“Although we do not have the final results of the pollution analysis, the Ministry of Environment recognizes that the pH of the water is normal,” Maranhao state Governor Carlos Brandao told TV channel CNN Brasil on Monday.

State and federal authorities have told cities that may be affected by the incident to avoid collecting water from the Tocantins River.