Associated Press

HOUSTON -- Counselors were at a Houston refinery Monday as crews returned to their jobs after a crane collapse left four contract workers dead.

Safety meetings are also scheduled.

Investigators are trying to determine what caused the accident at a Lyondell Basell refinery on Friday July 18, 2008. The 30-story-tall crane is owned by Deep South Crane & Rigging.

The four men who died worked for the Louisiana company.

Seven other workers were injured.

The refinery has video cameras at various sites. Officials hope some footage will bolster the investigation