SCOTTSBLUFF, Neb. (AP) — Scottsbluff police have been investigating reports that several children were injured when a school bus driver slammed on its brakes.

The incident occurred May 4 as around 20 students were being taken to Westmoor Elementary for an after-school program. Capt. Brian Wasson says there have been several reports the driver hit the brakes because he couldn’t get all the students to sit. Wasson said Friday that those reports haven’t been confirmed but also says investigators have obtained a digital and audio recording from inside the bus.

Wasson says several parents sought medical treatment for their children, but he doesn’t know of any student who required hospitalization.

A spokeswoman for the district’s bus service, First Student, says the driver is no longer employed. Wasson says no citations have been issued.