Oncoming winter conditions may make the landslide impossible if the measure is not successful in the coming days, reports NRK.
The section of the 1,294-metre peak in the Rauma municipality in Romsdalen is one of Norway's most closely-monitored for landslide risks.
Geologists refer to the unstable section of the Mannen mountainside as ‘Veslemannen' (‘The Little Man').
Veslemannen is about 1,200 metres above sea level and has a volume of 120,000 to 180,000 cubic metres - about one percent of the total volume of Mannen.
Heightened avalanche risk on the mountain dates back to 2014.
In an attempt to set off a controlled landslide, the Norwegian Water Resources and Energy Directorate (NVE) began pumping water into cracks in the mountainside during Monday night, reports broadcaster NRK.
“We are now again seeing a slight increase in movement,” NVE's Lars Harald Blikra told the broadcaster on Tuesday morning.
The mountainside has moved by 70 centimetres over the last week, reports the broadcaster – more than in the whole of 2016.
Movement had increased to 20 centimetres per day on Tuesday morning.
With landslide alert levels increased to 'red', local residents were evacuated on Sunday, clearing the way for NVE and local authorities to attempt to set off a landslide, writes NRK.
A drop in temperature between Monday and Tuesday slowed the movement of the loose terrain, but NVE hopes to speed things up again during Tuesday.
Weather forecasts currently suggest snowfall later in the week, which would make the work to move the unstable area more difficult, according to the report.
Freezing temperature and subsequent reduction of natural addition of water to the relevant area means that NVE's pumping of extra water is likely to be needed to initiate the controlled landslide.
“It is a little early to see how it will work out. We will continue adding water over the course of the day and evaluate its effects on an ongoing basis,” Blikra said.
Lars Olav Hustad of Rauma Municipality told NRK that he hopes the landslide will be set off on Tuesday.
“Residents are tired and fed up with the situation. They want it to be resolved. Now they will either move home again without the landslide happening or with it having happened. That is what they want the most,” he said.