(CNN)The deeper authorities dig in the aftermath of the airport and subway attacks in Brussels, the more tangled the web is.
For now, we know at least five people were involved.
It all points to a much bigger terror network than suspected. And investigators are playing catch-up, hoping there isn't another attack before they figure things out.
Here's where things stand:
The blasts went off during the morning commute Tuesday, in two places where the terrorists must have figured they could inflict maximum damage: The Brussels Airport around 7:58 a.m. and the Maelbeek subway station around 9 a.m.
At the airport
At least three people apparently took part in the airport attack:
• Najim Laachraoui, an ISIS bomb-maker who is suspected of involvement in the Paris attacks. He was one of the suicide attackers at the airport.
• Ibrahim El Bakraoui, who had been sentenced in October 2010 by a Brussels criminal court to nine years behind bars for opening fire on police officers with a Kalashnikov during a robbery. He also blew himself up.
• A third, unidentified man in a hat, caught in surveillance footage walking next to Laachraoui and El Bakraoui. He placed a bomb at the airport and left. Authorities later detonated the device in a controlled explosion.
At the metro station
Two people were involved in the metro station blast:
• Khalid El Bakraoui, Ibrahim's brother. He blew himself up as well. Interpol had issued a "red notice" for him that noted Belgian authorities wanted him in connection with terrorism. But it wasn't clear when that notice was issued or why Belgian authorities are saying he had no ties to terrorism.
• A second, unidentified man, whose whereabouts is unknown. We also don't know whether he's dead or alive.
Links to Paris
Officials think the Brussels attacks are linked to the ones in Paris in November, for at least two reasons:
• Salah Abdeslam: He was the sole survivor of the team responsible for the Paris attacks. After escaping Paris, he hid out in a Brussels apartment. Who rented the apartment, using false ID? Khalid El Bakraoui, the subway bomber.
• Najim Laachraoui, one of the airport bombers His DNA was found in houses in southern Belgium and Brussels that the terrorists behind the Paris attacks used.