A hydrogen emission was reported on Friday in Kokkola, a coastal town in central Finland, without casualties.
Initially, a sodium hydroxide leak in the Woikoski hydrogen production plant required rescue services to arrive and production was stopped.
As reserve hydrogen tanks in the compound were activated for interim customer deliveries, the system began leaking hydrogen to the environment.
Despite immediate danger, an explosion was averted, newspaper Keskipohjanmaa reported. There were no casualties.
An explosion was reported at the Woikoski plant in 2015.
Clas Palmberg, the owner of the company, told local media that "all incidents in a hydrogen plant have to be taken very seriously."