DENTON (CBSDFW.COM) –Three people are dead and traffic was backed up after two 18-wheelers and multiple passenger vehicles crashed on I-35W.

Three more people were injured and taken to the hospital.

READ MORE: Malik Faisal Akram 'Got Agitated' At Islamic Center Days Before Taking Hostages At Synagogue

“As we are working though this incident, we have been able to identify four vehicles and two 18-wheelers that were involved at this time, but as we continue to work through it, due to the state of the vehicles, all of those numbers may change,” said Khristen Jones with the Denton Police Department.

One of the two 18-wheelers involved was carrying butane tanks, which caused an explosion. Police found the driver walking by the road. He was stunned with only minor injuries.

READ MORE: FBI Warning To Faith Communities After Colleyville Synagogue Hostage Situation Familiar To Jewish Community

Firefighters and police officers responded Friday afternoon to the major crash in the 2300 block of I-35W. The grisly crash scene showed two cars atop the burned out semi-truck. There were fatalities in three of the burned out cars, including the two vehicles on the big rig. Police had to count the rims to discern how many vehicles were actually involved in the horrific crash. 

Both directions of traffic were closed until about 4 p.m. when the southbound lanes reopened. 

MORE NEWS: Cowboys QB Dak Prescott Apologizes For Taking Pleasure In Fans Pelting Officials After Playoff Loss

Police are still investigating but said they believe speed was a factor.