Context : Methanol masers at 6.7 GHz are well known tracers of high-mass star-forming regions ( HMSFRs ) .
However , their origin is still not clearly understood .

Aims : We aimed to determine the morphology and velocity structure for a large sample of the maser emission with generally lower peak flux densities than those in previous surveys .

Methods : Using the European VLBI Network ( EVN ) we imaged the remaining sources from a sample of sources that were selected from the unbiased survey using the Torun 32 m dish .
In this paper we report the results for 17 targets .
Together they form a database of a total of 63 source images with high sensitivity ( 3 \sigma _ { rms } =15–30 mJy beam ^ { -1 } ) , milliarcsecond angular resolution ( 6–10 mas ) and very good spectral resolution ( 0.09 km s ^ { -1 } or 0.18 km s ^ { -1 } ) for detailed studies .

Results : We studied in detail the properties of the maser clouds and calculated the mean and median values of the projected size ( 17.4 \pm 1.2 au and 5.5 au , respectively ) as well as the FWHM of the line ( 0.373 \pm 0.011 km s ^ { -1 } and 0.315 km s ^ { -1 } for the mean and median values , respectively ) , testing whether it was consistent with Gaussian profile .
We also found maser clouds with velocity gradients ( 71 % ) that ranged from 0.005 km s ^ { -1 } au ^ { -1 } to 0.210 km s ^ { -1 } au ^ { -1 } .
We tested the kinematic models to explain the observed structures of the 6.7 GHz emission .
There were targets where the morphology supported the scenario of a rotating and expanding disk or a bipolar outflow .
Comparing the interferometric and single-dish spectra we found that , typically , 50–70 % of the flux was missing .
This phenomena is not strongly related to the distance of the source .

Conclusions : The EVN imaging reveals that in the complete sample of 63 sources the ring-like morphology appeared in 17 % of sources , arcs were seen in a further 8 % , and the structures were complex in 46 % cases .
The ultra-compact ( UC ) H II regions coincide in position in the sky for 13 % of the sources .
They are related both to extremely high and low luminosity masers from the sample .