The death toll continues to grow in Seoul after people were crushed to death as a crowd surged in an alleyway during Halloween festivities.

At least 154 people are dead due to the crushing. An official said at least 82 people were injured, 19 of them seriously. Of the 154 dead, 22 were foreigners.

Most of the dead were teenagers or in their 20s. Witnesses said those trapped in the alleyway scrambled to get out of the suffocating crowd and piled on one another.

"At that level of density, it's no surprise that the first few people begin to faint, because they're too tight and they can no longer breathe," Mehdi Moussaid, a researcher in crowd behavior at the Max Planck Institute for Human Development, told the Washington Post on Sunday after reviewing some videos of the night.

"And if this continues, and that's what happened, then all the people in that zone will no longer have enough oxygen, even after they faint, and will die one after the other," Moussaid added.

The incident continues to be investigated.

At least two American citizens were reported dead. Three U.S. citizens have been reported injured.

"The U.S. Embassy in Seoul is working closely with local authorities and other partner organizations to assist U.S. citizens affected. We offer our sincerest condolences to the loved ones of those killed and continue to assist the injured. Due to privacy considerations, we have no additional details at this time," the U.S. Embassy told CNN.

Officials believe the festivities attracted a higher number of people due to Halloween celebrations returning after COVID restrictions.

President Joe Biden released a statement Sunday about the tragedy.

"Jill and I are devastated to learn that at least two Americans are among so many who lost their lives in Seoul. Our hearts go out to their loved ones in this time of grief, and we continue to pray for the recovery of all who were injured," Biden said.