The coincidence was observed between the places with weak (probably inverse) photospheric longitudinal magnetic fields in the big spot of the AR NOAA 8340 prior to the start of the flare and a common base of the giant arches (loops) and centers of emission visible in the HeI 10830Å line core during the flare. A number of observational facts compel us to make a supposition that the flare was the consequence of an injection of plasma from the places with marked peculiarity of the photospheric magnetic field into the expanding magnetic arcade.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html