Matatā fire chief Gavin Dennis said the crash was one of the worst his crew has had to deal with in his 32 years in the brigade.
The trauma of the tragedy had impacted not just the workers, survivors, and witnesses but also emergency service staff called to the incident, Dennis said.
"We are arranging counselling for all of our members," he said.
"We haven't had anything that tragic for a while but they, crashes, they're all traumatic. Every time we are called to a car or motor vehicle-related death or serious injury, it is always traumatic. But that ... we haven't had anything that tragic for a while."
Allan Dawson, managing director of Aongatete Coolstores, where five workers were killed in a 2016 SH2 crash, said accidents such as this "bring it all back".
Dawson said hearing the news of a multiple-fatality was poignant and a reminder for all his staff.
"You relive it."
A lot of the Tongan staff were getting ready for packing season now and many frequently visited the memorial at the packhouse for the five workers who lost their lives, he said.
A large portion of the Tongan staff and new ones coming over are friends or relatives of those who were tragically killed in 2016.