Stones were thrown at a number of trains in Wellington and Telford leading to windows being smashed, according to British Transport Police.
A police spokesman said on 5 April they received a report that three trains were hit by stones while travelling through Wellington.
On all three occasions, the stones broke the "outer skin" of some of the trains' windows.
One of the trains had to be taken out of service.
He said this resulted in delays and disruption to services in the Shrewsbury area.
On 6 April the driver of the 1405 BST Birmingham New Street to Shrewsbury service also reported that missiles thrown from a bridge known as the Zigzag Footbridge in Copperbeech Road, Telford, had smashed the outer skin of a window.
He said officers have stepped up patrols in the area and are also appealing for anyone with any information about these incidents, or who saw anyone acting suspiciously in the area, to come forward.
Sgt John Caisley said: "These dangerous incidents left the train drivers understandably shaken.
"We urge those who think that throwing stones and other objects at passing trains is fun to consider the consequences of their actions, which could have been much worse.
"Offenders who throw objects at trains not only risk seriously injuring passengers and staff but are risking a prison term."