Icelandic police restricted access to the volcano and residents of the Reykjanes peninsula were encouraged to shut windows and switch off ventilation, the department of civil protection and emergency management said late on Monday.

The Icelandic Met Office, Vedur, said on Tuesday morning that gas pollution was high and dangerous around the eruption, some 60 km (37 miles) from the capital, and pollution was likely in Reykjanes and Reykjavik.

However, air quality was still considered “very good” or “good” in the Reykjavik area on Tuesday, according to the Environmental Agency’s website.

Tuesday’s footage of the eruption showed that the fissure had shortened, lava flow had slowed and the gas plume was smaller, Magnus Tumi Gudmundsson, professor of geophysics at the University of Iceland, told the Icelandic broadcaster RUV.

“This has become a small eruption, which is very good news,” he said, adding it was still impossible to assess how long it would last.

“In all likelihood it won’t be big, it can certainly last a long time, but luckily we’re not looking at a continuation of what we saw in the first few hours,” he said.

The eruption follows intense seismic activity over the past few days and is classified as a fissure eruption, which does not usually result in large explosions or a significant amount of ash in the stratosphere, the Icelandic government said in a statement late on Monday.

Flights into and out of Iceland have not been disrupted.

(Reporting by Louise Breusch Rasmussen and Victoria Klesty; Editing by Robert Birsel, Devika Syamnath, Emma Rumney, Alexandra Hudson)