Federal investigators are looking into a crash that killed two road workers on I-95 in Waterville on Tuesday.

On Wednesday, the National Transportation Safety Board said it was sending investigators to conduct a safety investigation.

Maine State Police say a minivan driven by a 34-year-old woman ran through a temporary stop sign around 9:40 a.m. Tuesday on the on-ramp near mile marker 127 and was struck by a tractor-trailer.

The van then crashed into three MaineDOT workers, killing 60-year-old James Brown and 51-year-old Dwayne Campbell, both from Waterville.

The two were thrown over the bridge and pronounced dead at the scene.

On Wednesday, MaineDOT said two other workers are recovering after suffering non-life threatening injuries.

Shannon Moss with the Maine Department of Public Safety says their investigation could take a month or more due to the complexity of the accident.

The investigation will then be turned over to the District Attorney’s Office to determine if any charges will be filed.