The U.S. Department of Transportation on Wednesday ordered the suspension of all passenger and cargo flights between the United States and Venezuela, citing reports of unrest and violence around airports in the South American country.

In a letter to the Transportation Department requesting the halt, the Department of Homeland Security said “conditions in Venezuela threaten the safety and security of passengers, aircraft, and crew traveling to or from that country.”

Venezuela’s information ministry did not immediately respond to a request for comment.

Many international airlines had stopped flying to Venezuela anyway because of security concerns and disputes over money they say the government owes them.

American Airlines Group Inc., previously the largest carrier providing service between the United States and Venezuela, in March said it was indefinitely suspending its flights to Venezuela.

Air Canada stopped flying to and from Venezuela in 2014, citing “civil unrest.”

In April, the U.S. Federal Aviation Administration prohibited U.S. air operators from flying below 26,000 feet in Venezuela’s airspace.

The administration of U.S. President Donald Trump last week expanded the scope of its Venezuela sanctions to the defence and security services sectors to try to crank up economic pressure on President Nicolas Maduro.

The moves are part of a four-month-old campaign against Maduro as the United States ramps up its support for opposition leader Juan Guaido.