NORFOLK, Va. (AP) — An SUV hit a patch of ice on westbound Interstate 64 in Virginia, triggering a 75-car pileup last month, investigators said.

Virginia State Police said in a news release that the driver of a 2008 Chevrolet SUV spun out and was hit by other vehicles at the start of the pile-up shortly before 8 a.m. on Dec. 22, The Virginian-Pilot reported on Friday.

The crash occurred at the Queens Creek Bridge in Upper York County and shut down the interstate for over seven hours. Officials said 51 people in were injured.

State police initially reported 30 vehicles were involved in the crash before announcing the total of 75 on Friday.

An eight-vehicle crash happened on the eastbound side of I-64 near mile marker 240, Virginia State Police spokeswoman Sgt. Michelle Anaya said on Dec. 22.

Ryan Rogers, a National Weather Service meteorologist at Wakefield, said visibility was poor around the time of the crash. At the nearest weather station in Williamsburg, fog had reduced visibility to less than a quarter-mile 20 minutes before the crash.

Rogers said it was possible freezing fog — supercooled water droplets that can freeze instantly — had impacted the bridge.

No charges have been filed, and police said the investigation continues.