Costa Rica’s government issued an emergency alert Sunday after a ship carrying nearly 200 tons of toxic chemicals capsized off the Central American country’s Pacific coast. Officials briefly warned the public to avoid entering the waters along about 60 miles of coastline until they could determine the spill’s breadth and potential effects.

The ship spilled its payload of ammonium nitrate -- a chemical commonly used to make explosives and fertilizers -- in rough waters Saturday near the town of Puntarenas, the BBC reports. An alert was issued “because of the potential impact ammonium nitrate could have on human health,” Costa Rica National Emergency Commission (CNE) spokesman Reinaldo Carballo said in a statement.

Costa Rican officials remain unsure how much ammonium nitrate remains in the spill zone or how far the chemicals may have spread. Local fishermen were also encouraged to avoid the area. Two crew members were rescued from the accident site, Al Jazeera reports. The spill reportedly reached the Costa Rican port of Puerto Caldera, though it’s unclear what damage, if any, was done to the area.

“Authorities hope the product [ammonium nitrate] has been diluted in the gulf waters, and that currents have taken it out to open sea. However, it’s necessary to conduct a series of laboratory studies to rule out any type of damage it could cause,” the CNE said in a statement, according to Costa Rican news agency the Tico Times.

The CNE first classified the alert as “red” but downgraded it to “yellow” after initial tests were completed. Officials said it was safe for swimmers to return to local waters, though it could be days before workers complete their investigation into the incident.

“What we’ve seen are a few dead fish. We’re calling for calm,” Maria Fulmen, Costa Rica’s vice minister of public security, said at a press conference, according to the Tico Times.