Arch removal on load bearing wall

[Radders_23]

Hi all, we have moved into a 1950s house and want to square off an archway. However I can't work out how it's constructed. Having exposed the plaster as best as I can I can see a rounded tile (?) structure that's then been shallowed out giving a smaller archway. The bit in between that and the line crack sounds hollow. As this is a load bearing wall am I ok to square this off and how would I do this?

 

[arkie]

Hope the arch is just wood and plasterboard, Or a pre-made plaster arch you screw on, Hammer and old wood chisel to remove the plaster to find out whats under it.

 

[noseall]

There is a definitive horizontal crack running the length and above the arch. This probably demarcates the connection between cosmetic and constructional openings.

Get your hammer out.

 

[Radders_23]

Should I worry about there being a lintel there to support the wall above or can I hope to find this further under the plaster?

 

[oldbutnotdead]

Plaster isn't load bearing so chopping it off with hammer and bolster won't make the place fall down.
Reckon @noseall is right about that crack- start chopping plaster just below it.