Flights to and from Rīga International Airport are among those in Europe that have been canceled because of a volcano in Iceland that is spewing ash into the atmosphere.

In an announcement on the airport’s Web site, officials said that all flights from midnight to 6 p.m. on April 16 have been canceled. Latvia’s airBaltic canceled flights to numerous destinations April 15 and 16, including Helsinki, Oslo, Brussels, Copenhagen, Tallinn, Hamburg, Stockholm and other locations.

Flight cancellations began April 15 in the United Kingdom as the ash spread southeast from Iceland. The National Air Traffic Services said flight restrictions will remain in place until at least 7 p.m. April 16 U.K. time. Some flights may be allowed, depending on meteorological forecasts.

“In general, the situation cannot be said to be improving with any certainty as the forecast affected area appears to be closing in from east to west,” NATS announced on its Web site.

Similarly, flight operations over Sweden were shut down April 15, including the flagship Stockholm Arlanda Airport.

“The forecast is that the situation will be the same during Friday (April 16),” airport officials announced on the airport’s Web site. “Most likely there will be very large disturbances in air traffic then as well.”

The ash is from the Eyjafjallajökull volcano in south Iceland. The eruption began on March 20, according to the Icelandic Meteorological Office. After quieting for a few days, activity at the volcano started again April 14, sending a plume of smoke and ash at least 8 kilometers into the air.

Jet stream winds have carried the ash southeast to the United Kingdom and continental Europe, where aviation officials are concerned about damage the ash could do the aircraft engines. However, the Latvian Environment, Geology and Meteorology Centre said the ash should not be a health concern.