The body recovery at a construction site near Phoenix Sky Harbor Airport has entered its fourth day Thursday.

Crews have removed over 50 tons of dirt from the site but have been unable to find the missing construction worker, who is presumed dead.

The 300,000 pound drill rig fell during construction of a guideway system for the Phoenix Sky Train Monday around 9:30 a.m. Since then, a number of specialty equipment has been brought in, including a large crane the length of 10 semi trucks, but progress is slow.

According to Captain Jake Van Hook of the Phoenix Fire Department, the ground around the downed drill is unstable and “for every one foot of depth, crews are needing to remove between two and three feet of width in every direction.”

The name of the construction worker has not been released.