Minesweepers have reportedly destroyed a suspicious package at the airport, according to news site Aveneir, citing police sources. Authorities had earlier reestablished a security cordon at Zaventem airport following the discovery of a suspicious package.
During raids in the district of Schaerbeek, police also found an explosive device.
"The searches…have led to the discovery of an explosive device containing nails, among other things," reads a statement from the prosecutor's office. "The investigators have also discovered chemical products and an Islamic State flag."
Earlier, Belgian federal prosecutor Frederic Van Leeuw warned that there may be additional controlled detonations of suspicious packages.
Nearly 600 flights have been cancelled as a precautionary measure. Local media reports that six police officers were wounded during the attacks, one them of seriously.
Cities across the globe have expressed solidarity with Brussels in the wake of the attacks. One World Trade Center in New York City, the Eiffel Tower in Paris, and Burj Khalifa in Dubai will all be lit red, yellow, and black on Tuesday night.
"The terror attack in Belgium is possibly the most difficult and most tragic in all of the history of Brussels and all of Belgium," Belgian Prime Minister Charles Michel said.
King Philippe of Belgium also addressed the nation on Tuesday, saying "we are so grateful for all those who have helped."
"We are faced with a threat, but we will continue to work together calmly, surely and with dignity," he said. "We must continue to trust ourselves. This is our strength."
