DENVER -- The private Oregon company that lost four employee firefighters when a van crashed en route to a central Colorado fire will not send new crews to fight wildfires while workers grieve, officials said.

Four people were killed and seven injured when the van carrying employees of Grayback Forestry Inc. rolled on Interstate 70 in western Colorado on Friday afternoon. Three remained hospitalized, one in critical condition.

Fifty-four other Grayback employees who were traveling to Colorado returned home Saturday night, company owner Mike Wheelock said Sunday.

"The reason we're doing it is to give time for the families to grieve, and to re-evaluate our procedures," he said. "We've got four people dead, and we've got people really upset. We're just trying to use all of our management to deal with that."

About 120 Grayback workers already on the lines at the 137,000-acre Hayman blaze, and about 180 fighting fires elsewhere, will remain in place, Wheelock said.

The company remains in good standing with the federal government, and there was no pressure for it to suspend new operations, said Nancy Lull, spokeswoman for the National Interagency Fire Center in Boise, Idaho.

Wheelock said no employees of his 23-year-old company had ever suffered a death or serious injury until Friday. He said he would re-examine procedures.

"We felt we had one of the best safety policies in the industry, and we're just going to upgrade that and go from there," he said.

The U.S. Forest Service, which contracts with the company, decides how workers will travel, Wheelock said.

The Colorado State Patrol said the van driver, Megan Helm, 21, of La Grande, Ore., has been issued a summons to appear in court on charges of careless driving causing death and careless driving causing serious injury.

Killed were Retha Shirley, 19, and Daniel Rama, 28, of Baker City, Ore.; Jake Martindale of Boise; and Zachary Zigich of Twin Falls, Idaho.

Those in serious condition are 20-year-old Brandon Fiala of Twin Falls, Idaho, and 25-year-old Anthony Kyle of La Grande, Oregon. Bartholomew Bailey, 20, of Corvallis, Oregon remains in critical condition.

Forest Service officials are investigating whether fatigue played a role in the crash.

The crew was on what was to be a 30-hour nonstop drive from Oregon.

Wheelock said all of the people who drive his vans, including Helm, are licensed under a federal law that requires a background check, a review of the driver's record and regular drug tests.

More than 200 firefighters gathered outside Lake George Community Church Sunday night to honor the four fighters who were killed in that accident. Townspeople applauded as firefighters filed in for the service.

So many attended that the ceremony had to be held outdoors.

Some residents told 7NEWS that there was nothing that could stop them from attending the memorial.

"They didn't know us. So I had be to here to say, 'You were coming to help me and you didn't make it. And God's going to protect you for it,'" said Lake George resident Paul Reagan.

"These young people have fought so valiantly for our homes and we felt it was critical to be here to show our support for their family and friends," homeowner Julia Reagan.

After the service, residents shook hands with firefighters as they filed back to camp. One said that it was the first time they couldn't smell smoke in two weeks.