Multiple grass fires that grew to burn more than 130 acres near the small town of Louviers in Douglas County were likely caused by a passing train, according to the Douglas County Sheriff’s Office and the South Metro Fire Rescue Marshal’s Office.

Firefighters reached 100% containment of the “Airport Fire” on Wednesday. No injuries or structural damage were reported in the over three-day blaze.

“Following a thorough investigation by the South Metro Fire Rescue Fire Marshal’s Office, evidence indicates that the brush fire was ignited by activity associated with a passing train,” a Douglas County Sheriff’s Office spokesperson told The Denver Gazette in an email on Thursday.

“Investigators identified ignition indicators and have video evidence along the rail line consistent with passing train operations,” the spokesperson said. “No other ignition sources were found in the area.

In a statement on Wednesday, sheriff’s office officials called full containment a “milestone,” recognizing “tireless efforts of all the fire crews, support personnel, and agencies who worked around the clock to protect lives and property.”

The fire began as a brush fire on Sunday around 2 p.m., near 9844 Titan Court near Airport Road, leading authorities to dub it as the “Airport Fire.” The area is located just south of Chatfield State Park.

South Metro Fire Rescue authorities and the Douglas County Sheriff’s Office quickly ordered an evacuation of the entire town of Louviers on Sunday, resulting in the evacuation of 39 homes. The order was lifted hours later, after Douglas County’s wildfire response helicopter dropped rounds of water and on-the-ground crews began containing the flames.

The fire ultimately encroached and threatened nearby homes. The flames stretched about six miles long and created hot spots along the train tracks running through town, according to fire officials.

“The area of origin aligned with the train’s path at the time of the fire,” the sheriff’s office spokesperson said.

The fire reached 90% containment on Sunday night. During the day, Douglas County’s wildfire response helicopter dropped 88 rounds of water totaling 26,400 gallons, sheriff’s office officials reported.

Many other departments in the metro Denver area responded to the fire, and over 130 personnel assisted at the scene.

Firefighters continued to contain the blaze on Monday, discovering more hot spots along the way. On Tuesday, a new brush fire burned around five acres in open space near 6005 Ron King Trail east of Santa Fe Drive.

On Wednesday, thunderstorms and heavy rain fell in the area.

“Mother nature’s favorable weather conditions helped support containment efforts,” sheriff’s office officials said.

Authorities warned containment doesn’t mean the fire is fully extinguished, adding that fire hot spots remain and will be closely monitored.