Two self-described heroin addicts are under arrest in eastern Missouri, accused of stealing a truck that was transporting 2,000 mice used for medical research.

The St. Louis Post-Dispatch reports the heist occurred in St. Charles around 3:20 a.m. Wednesday in the parking lot of a Red Roof Inn.

Hotel staff told police they saw two men smash the window of the 2008 Freightliner and take off toward Interstate 70. The transport company tracked the vehicle with GPS, and police stopped it a short time later in Bridgeton.

The truck's driver had left it running to keep the cargo cool. The mice, valued at $10,000 were unharmed.

Police said the suspects told investigators they took the truck to help support their heroin addictions.