Shenandoah County Public Schools are closed Tuesday after a tractor trailer crash on Interstate 81 near mile marker 285, north of Woodstock. The deadly wreck closed both directions of the interstate for several hours, though northbound lanes have now reopened.

Both directions of the interstate were closed for several hours. Northbound lanes reopened around 8:30 a.m., but the southbound lanes remained closed while officials examined the extent of the damage and cleared debris from a four-vehicle accident that involved three tractor trailers and one car.

According to a Virginia Department of Transportation release, the southbound lanes reopened around 3:30 p.m. after crews cleared and washed the road to see what damage the chemicals from one of the trailers and the fire did. VDOT reported an eight-mile backup when it reopened the road.

Officials at the site say much of the day was spent clearing the accident and working with the HAZMAT truck. The pavement in the southbound lanes had to be washed to remove all HAZMAT chemicals. A small containment area in the median is being used to hold the washed material before it can be removed from the area.

VDOT officials examined the pavement and determined that there is no damaged from the heat from the vehicle fire

According to Shenandoah County authorities, three people died in what fire officials are calling a three-alarm accident. More than five fire and rescue squads responded to the scene late Monday night.

Emergency efforts were hindered because of a corrosive material one of the tractor trailers contained that caught fire.

HAZMAT crews from Harrisonburg responded to the scene to assist in the cleanup.

Officials say people in cars near the accident were evacuated because of concerns about smoke coming from the chemical fire that resulted from the crash. The Red Cross cared for these people as some complained of respiratory problems.

At this point, first responders aren't sure what caused the crash.

Bobby Funkhouser, from the Woodstock Fire Department, says, "I know it was foggy, very foggy. We're not sure if a wreck occurred, others got out to help and got hit in the process, or what happened but fire wreck, we're not sure. It's just one of those things where the investigation to the accident will come in from the state police."

Police have not yet releases any information on the victims. They are also still working on what caused the accident.

Investigators are searching the scene for clues, including checking the parts of the wreckage, in order to reconstruct the crash.