HARRISBURG, Pa. -

State police said they investigated 900 crashes during the busy holiday travel period between Tuesday and Thursday.

Two of the biggest crashes happened in the Berks County area Thursday morning.

More than 40 people were injured, two critically, in a series of accidents involving several tractor trailers and other vehicles on Interstate 78 in Greenwich Township, police said.

Thirty-five vehicles were involved in four clusters of accidents on the Pennsylvania Turnpike in Brecknock Twp., Lancaster Co., near the border with Berks County. As many as 10 people were injured in those crashes, police said.