An Air France flight bound for Detroit was diverted to Montreal on Wednesday afternoon due to concerns that one of the passengers on board may have been exposed to the Ebola virus.

According to U.S. Customs and Border Protection (CBP), the passenger was allowed to board Air France flight 378 in Paris “in error” after recently being in East Africa, which is currently dealing with a rare type of Ebola virus.

“Due to entry restrictions put in place to reduce the risk of the Ebola virus, the passenger should not have boarded the plane,” read a statement sent to CityNews. “CBP took decisive action and prohibited the flight carrying that traveler from landing at Detroit Metropolitan Wayne County Airport, and instead, diverted to Montreal, Canada.”

Officials would not say if the passenger was showing any signs or symptoms of the virus.

According to flight tracking platform FlightAware, the flight landed in Montreal at 5:15 p.m., and the passenger in question was escorted off the plane. The flight was then allowed to continue to its destination in Detroit, where it landed just after 8 p.m.

On May 18, the CDC and the U.S. Department of Homeland Security announced a 30-day travel ban on non-U.S. passport holders from the Democratic Republic of Congo, South Sudan and Uganda, as well as screenings at airports and other points of entry for all travelers who departed from airports in those countries or have visited them in the last 21 days.

In a statement, Air France confirmed that a Congolese passenger on board was denied entry into the United States.

“Under new regulations, passengers arriving from certain countries, including the Democratic Republic of the Congo, may only enter U.S. territory via Washington (IAD) Airport,” the statement said. “There was no medical emergency on board, and like all airlines, Air France is required to comply with the entry requirements of the countries it serves.”

The World Health Organization (WHO) has declared the outbreak a public health emergency of international concern, worried over its “scale and speed.”

So far, 51 cases have been confirmed in Congo’s northern provinces of Ituri and North Kivu, and two cases in Uganda, WHO Director-General Tedros Adhanom Ghebreyesus said Wednesday. There are 139 suspected deaths and almost 600 suspected cases.

The London-based MRC Centre for Global Infectious Disease Analysis estimated that cases have been substantially undercounted and that the actual number could already exceed 1,000.

Files from The Associated Press were used in this report