(S (S (S (NP (BASENP (DT A) (NN shop)) (PP (IN on) (BASENP (PRPD its) (NN ground) (NN floor)))) (VP (VBD was) (VP (VBG undergoing) (BASENP (NNS renovations))))) (SBAR (WHADVP (WRB when)) (S (BASENP (DT the) (NN building)) (VP (VBD collapsed))))) (PERIOD .))