Gunfire and explosions were heard on Monday at the Westgate shopping complex in Nairobi, Kenya, where terrorists launched an attack three day ago and continue to hold hostages.

A security official told Reuters that it was the Kenyan security forces, not the terrorists who caused the explosion this morning. “[W]e are trying to get through the roof,” he said.

There have been a number of statements by security forces that the attack should be coming to an end, however, the attackers, terrorists from the Somalia-based Al-Shabaab group, remain at large. Al-Shabaab has demanded that Kenya pull its troops out of Somalia, warning they would kill hostages if Kenyan forces, aided by Israel and Western powers, tried to attack.

According to CNN, it is not known if any hostages still remain in the building, but if there are, the number is expected to be very small. When the siege began, the attackers went from store to store, taking hostages and killing others—specifically, targeting non-Muslims.

There have also been claims that US citizens, those a part of Al-Shabaab of American citizens, participated in the attack. The Federal Bureau of Investigation (FBI) has not yet confirmed if this is true or not.