Schools in the Groningen town of Oude Pekela remained closed on Tuesday as firefighters continued to tackle a massive fire at a hemp processing plant that has been burning since Monday evening.

The fire broke out in the storage area of Hempflax at around 8.30 pm and quickly spread. Several nearby homes were evacuated, and 20 people were forced to spend the night elsewhere.

Residents have been advised to keep doors and windows closed due to the smoke.

Hempflax produces hemp-based products including building materials, animal care items, and food supplements. Tens of thousands of bales of hemp straw, harvested last year, were stored in the affected area.

“We only harvest once a year and have to store everything,” a company spokesman told RTV Noord. “The bales are as dry as tinder.”

The town’s schools have been closed because of falling ash, which has been covering homes and gardens. Tests showed the ash did not contain asbestos, the town council said on Tuesday.

The cause of the fire has not been established but it could not have been a short circuit because there was no electricity in the building, the company told RTV Noord.