A plane crashed in Costa Rica on Sunday, killing at least 12 people – with 10 of them US citizens – the country’s security ministry said.

The crash, the cause of which is not yet known, took place in the mountainous area of Punta Islita, which is popular with tourists, in the province of Guanacaste, about 140 miles west of the capital of San José.

Enio Cubillo, director of Costa Rica’s civil aviation agency, said those killed included 10 foreign tourists and two Costa Rican pilots.

The aircraft was operated by Nature Air, a local company which could not immediately be reached for comment.

Smoke rises from the site of the plane crash in Punta Islita, Guanacaste, Costa Rica. Photograph: AP

Laura Chinchilla, who was president of Costa Rica from 2010 to 2014, said on Twitter that her cousin was one of the crew members who had died in the accident.

The US state department said it was working with Costa Rican authorities.

“There are no people alive,” security minister Gustavo Mata said. He added that postmortems would be needed to confirm the total number and identities of victims because their remains were badly burned.