North Korea has banned foreigners from taking part in a marathon scheduled for April, citing concerns over the spread of Ebola, according to media reports. The government had closed the country’s borders to foreign tourists in October to keep the virus out of its territory.  

Nick Bonner, of Beijing-based travel agency Koryo Tours, said on Monday that he would have to turn away over 400 foreign runners who signed up with his agency for the event, after being informed by officials that the race would only accept local runners, The Associated Press reported.

“It is still unclear when the borders will be reopened, but we were also advised not to cancel our March tours, and to expect an update on the border situation at the end of February,” Bonner said on Monday, according to a report by The Guardian. 

The race, which consists of several courses in the city of Pyongyang, was opened to foreigners for the first time last year, and was reportedly a major success. Bonner said the group that had signed up for the race was the biggest his agency had put together in 10 years.

North Korea has banned nonessential travel since announcing the Ebola countermeasures, and all foreigners, including diplomats and aid workers, are subject to quarantine under medical observation for 21 days. So far, no cases of Ebola have been reported anywhere in or near North Korea, which is over 8,000 miles from the epicenter of the disease.

In recent years, North Korea has set up a number of tourism zones and bolstered international ties in an effort to bring in tourism revenue. According to Koryo Tours, business comes primarily from Chinese tourists, who account for tens of thousands of tourists every year.