A semi-truck crashed into the median of Interstate 25 near Castle Rock on Monday, shutting down the northbound highway, according to state troopers.

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A little more than a mile south of Plum Creek Parkway in Castle Rock, two semi-trucks are blocking northbound I-25, said Colorado State Patrol Trooper Sherri Mendez. She said one of the tractor-trailers crashed into the median, but it was unclear why the second was blocking several lanes of the highway.

According to Colorado Department of Transportation road cameras, traffic at the scene was at a standstill at 10:50 a.m. while crews worked to move the semitrailers out of the way. Several Waze users reported that the traffic jam spread from Exit 181 to Plum Creek Parkway to Exit 174 to Tomah Road near Dawson Butte.

Northbound I-25 is covered in snow at the scene of the accident, but investigators are unsure whether wintry weather conditions caused the accident.