The Costa Rican government says that a plane believed to be carrying 12 people has crashed in a wooded area.
Two Costa Rican crew members and 10 foreigners were on board, the ministry said.
Authorities said they were focusing on recovering the victims' bodies and would begin an investigation into the cause of the crash first thing Monday. Everyone on board the aircraft was killed.
Images posted by the country's public security ministry showed blackened wreckage, some in flames, with only part of the tail recognizable.
A U.S. State Department spokesperson confirmed that multiple U.S. citizens died in the crash.
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He added that social movements that start on the streets don't always remain under the control of those that started them. The semiofficial Ilna news agency reported there were smaller protests in Neyshabour, Kashmar, Yazd, and Shahroud.
"There are no survivors", the daily La Nacion said, citing Security Minister Gustavo Mata.
Dawn and Matthew Wolfe, who have been vacationing in Costa Rica for a month, said they and their three children were sitting in a restaurant near Punta Islita Airport when the plane took off.
"You will remain in our hearts, dear Juan Manuel Retana", she wrote.
This time of year is particularly busy in Costa Rica's coastal resort areas, which are especially popular with Americans looking to flee freezing weather conditions at home in search of tropical climates.