STOCKHOLM (AP) — Swedish police say they have no clues about possible perpetrators or motive two days after nuclear officials found a small amount of explosive material on a forklift at Sweden’s largest nuclear power plant.

Police spokesman Tommy Nyman says officers completed a search of the Ringhals plant area early today and were analyzing witness statements and security camera footage of the vehicle’s movements. He declined to give details.

Power utility Vattenfall said the clay-like, fist-sized explosive was found during a routine check as the forklift was entering the high-security enclosure, where the four reactors are situated, from the plant’s adjoining industrial area.

Sweden increased its security alert at the country’s three nuclear plants after Wednesday’s incident.