Three suspects who shot at a high-speed Deutsche Bahn ICE train with an air rifle are still at large, a federal police spokesman said on Tuesday.

Authorities have not yet been able to identify the men, and are asking witnesses to come forward with any possible clues. The men are being investigated for dangerous interference with railway traffic.

Read more: If you want German trains, go to Switzerland

Hidden in a wooded area outside of Frankfurt, the men shot at the passenger train with at least one air gun on Monday as the train was traveling on its way to the western city of Essen around 3:30 p.m. local time.

Several windows on the train were damaged during the shooting, but none of the 400 passengers were wounded.

Read more: Drunken train driver halted by German police

"Fortunately, none of the windows were penetrated and no passengers were injured," a police spokesman told local public broadcaster Hessenschau on Monday.

Following the air rifle assault, the damaged train is being inspected by forensic detectives for further clues. The results of their investigation should be ready by Thursday, a police spokesman told German news agency DPA.

rs/tj (AFP, dpa)