DENVER (AP) — A rash of hash oil explosions is prompting lawmakers in Colorado and Washington to consider spelling out what’s allowed when it comes to making hash or concentrated marijuana at home.

Both states have seen an increase in home fires and explosions linked to amateurs making hash — concentrated marijuana that can be inhaled or eaten.

Washington’s proposal would ban amateur hash cooks from using butane or other explosive gases, though safer methods would be allowed. Colorado lawmakers are considering similar limits.

Concentrated marijuana is increasingly popular because it can be mixed with food and made at home more cheaply than buying it from a commercial dispensary.