Enio Cubillo, Director of the Civil Aviation Authority, speaks during an interview with Reuters about the details of the investigation into the crash that killed two pilots and 10 U.S. tourists last week, in San Jose, Costa Rica January 4, 2018. REUTERS/Juan Carlos Ulate

SAN JOSE (Reuters) - Costa Rican authorities raided the offices of Nature Air on Monday, part of the investigation into a New Year’s Eve plane crash that killed two Costa Rican pilots and 10 Americans.

Chief investigator Walter Espinoza told reporters that the offices of Costa Rica’s civil aviation agency were also raided, describing both operations as routine to collect information.

He said it is still too soon to speculate on what caused the Cessna 208B Grand Caravan to plummet from the sky shortly after takeoff in the mountainous area off the Punta Islita beach town in the province of Guanacaste, about 140 miles (230 km) west of the capital San Jose.

Enio Cubillo, the director of the civil aviation agency, said last week that it could take months to determine the cause of a plane crash.

He said experts from the U.S. National Transportation Safety Board and Federal Aviation Administration, along with representatives from Cessna, the company that made the plane, are assisting with the probe.

Investigators are focusing on the weather conditions at the time of the crash, possible mechanical failures and human error.