The Canadian Border Services Agency says four of its officers were hospitalized Friday morning after being exposed to an unknown substance.

The border agents were investigating a vehicle and its occupants near the Peace Bridge in Fort Erie at around 6 a.m. when they opened two bags discovered in the car.

Fire officials in Niagara Falls told CTV News Toronto that it’s possible the “illicit substance” was fentanyl or crystal meth.

The officers were taken to hospital for a decontamination procedure as a precaution. Two were taken to a hospital in Welland, Ontario and the remaining two were transported to a Niagara Falls-area hospital.

No one was injured as a result.

“It sounds like there was two bags that were opened up or looked at that were potential hazards,” Niagara Falls Fire Chief Jim Boutilier said. “It was precautionary. Everything that was done here in Niagara Falls was done on a precautionary measure to ensure the safety of the staff.”

The CBSA says the investigation is ongoing.