A preliminary report was released Monday by the National Transportation Safety Board (NSTB) regarding the circumstances that led to the deadly Amtrak crash in Chester, Pennsylvania that killed at least two workers and injured another 80.

The report indicated that the agency's investigators are still determining the types of worker protections that were in place, if there are any, when the crash occurred on April 3 that involved 89 workers and a backhoe.

A report from the Wall Street Journal mentioned about a one-sentence caveat that figures at the center of labor disputes early this month. It refers to the fact that Amtrak is at odds with its workers about safety procedures.

According to the preliminary report of the NSTB, the train coming from New York City going to Savannah, Georgia with 341 passengers was travelling at 106 miles per hour when it struck two workers on the track. The train has a speed limit of 110 mph.

The two workers operating a backhoe at the crash scene who were killed were Joseph Carter Jr., 61 of Wilmington, Delaware and Peter John Adamovich, 59 of Lincoln University, Pennsylvania.

A separate report also revealed that the backhoe operator has a right to be on the tracks periodically during the weekend, said federal crash investigators on Monday.

In its latest report about the accident, the National Transportation Safety Board said the track where the accident happened was shut down at times during a 55-hour maintenance window.

It was not clear if trains were not permitted on these particular tracks when the crash occurred.

"NTSB investigators are confirming what roadway worker protections were in place at the time of the accident," said the agency.

The impact of the crash derailed the train's lead engine which carried 341 passengers and at least seven crew members. Over 40 people were hospitalized due to the crash; most of them sustained minor injuries such as bruises and scrapes.