TRINIDAD, Colo. (AP) — A railroad crossing in southern Colorado where five family members, including three young girls, were killed when an Amtrak train slammed into their minivan had been targeted for safety improvements for years.

The rural crossing near Trinidad, about 15 miles from the New Mexico border, was identified for improvements as part of ongoing work with counties and railroads to fix problem areas, said Amy Ford, a spokeswoman for the Colorado Department of Transportation.

Las Animas County commissioners approved a joint application for the work with the state just two weeks ago. But the proposal still has to be approved by the state Public Utilities Commission before work can start, county administrator Leeann Fabec said.

"I don't know what took so long," Fabec told the Denver Post on Monday. "That crossing has been there for probably 80 years. It's a rural road that's heavily used. I'm surprised myself that it took so long to come to the forefront."

State transportation officials began examining the site in late 2013 and targeted it for a significant safety overhaul, according to newspaper. The project would add flashers, gates, bells and a constant warning system at the at-grade crossing, which currently is marked only with signs.

A 4-year-old girl was the only member of her family to survive after the Southwest Chief train headed from Chicago to Los Angeles hit the van as it crossed the tracks Sunday morning. She was hospitalized with serious injuries.

The girl's father, 32-year-old Stephen Miller, who was driving, and his wife, Christina Miller, 33, of Trinidad were killed along with their three other daughters, aged 6, 2 and 8 months.

The Millers were on their way to church at the time.

"When they didn't show up for church, we were worried about what was going on," Keith Schlabach, Christina Miller's cousin, told the Post on Monday. "We thought they were broken down or something. One of the other guys was driving back from church toward Steve's house to see what happened, and then he got to the tracks."

Amtrak spokesman Marc Magliari said investigators are using the train's event recorder, similar to an airplane's "black box," to determine if the engineer sounded the horn before passing through the crossing,

"These incidents are always troubling and tragic," Magliari said. "We would have been across that crossing in a minute or less. That's what's so sad about this."

There have been six other accidents between vehicles and trains at the same crossing in the last 30 years, including one other fatal crash in 2010, according to Federal Railroad Administration records.