Four workers at the LyondellBasell refinery were killed and seven others injured when the massive crane crashed to the ground at around 1:20 p.m. Friday afternoon. Investigators said they would study surveillance camera footage of the refinery to gain information about the accident, the Houston Chronicle reported.

"We will ensure we do a full investigation to understand exactly what happened to cause this tragedy," Jim Roecker, divisional vice president of Houston refining for LyondellBasell, told the newspaper. "It's a very sad day for us here at the refinery. Certainly our thoughts and prayers go out to the families."

The International Union of Operating Engineers identified two of the victims as crane operators Marion "Scooter" Odom of Highlands, Texas, and John Henry of Dayton, Texas. A spokeswoman for the U.S. Occupational, Safety and Health Administration told the Chronicle that an investigative team was at the scene Saturday.