BRUSSELS (AP) — A Belgian prosecutor says police raids are happening around the country after two men “probably” staged suicide bombings at the Brussels airport and a third fled. The prosecutor says the third suspect is actively being sought by police.

At least 31 people were killed and nearly 190 wounded in the two airport bombings and another in the Brussels subway system.

Prosecutors say a house search in the Brussels neighborhood of Schaerbeek has “led to the discovery of an explosive device containing among other things nails.” Investigators also found chemical products and an Islamic State flag.

Their statement said the Islamic State group had claimed responsibility for today’s deadly attacks at the Brussels airport and a subway station via a press agency but that this information still needs to be verified.

Prosecutors say it’s not possible at this stage to establish any links between the attacks and those in Paris on Nov. 13 that left 130 people dead.

Prime Minister Charles Michel said the country will tighten security at its borders. He declared three days of national mourning after what he says were probably the most tragic attacks the country has seen in peacetime.

Thank you God for keeping me safe during these attacks in Belgium missed the explosions by minutes#brusselslockdown pic.twitter.com/YuPRyIk0Cf

— Brad Waldow (@bradwaldow) March 22, 2016