A storage silo in Oppau, Germany, <a href="https://en.wikipedia.org/wiki/Oppau_explosion" id="mwdg" rel="mw:WikiLink" title="Oppau explosion">explodes</a>, killing 500–600 people.<sup about="#mwt45" class="mw-ref reference" data-mw='{"name":"ref","attrs":{},"body":{"id":"mw-reference-text-cite_note-7"}}' id="cite_ref-7" rel="dc:references" typeof="mw:Extension/ref"><a href="./September_21#cite_note-7" id="mwdw" style="counter-reset: mw-Ref 7;"><span class="mw-reflink-text" id="mweA">[7]</span></a></sup>
<span class="mw-reference-text" id="mw-reference-text-cite_note-7"><cite about="#mwt42" class="citation web cs1" id="mwB94"><a class="external text" href="https://www.aria.developpement-durable.gouv.fr/wp-content/files_mf/FD_14373_oppau_1921_ang.pdf" id="mwB98" rel="mw:ExtLink nofollow">"French Ministry of Environment, Explosion in a nitrogenous fertiliser plant, ARIA 14373"</a> <span class="cs1-format" id="mwB-A">(PDF)</span>. <i id="mwB-E">ARIA</i>. <a class="external text" href="https://web.archive.org/web/20230806185119/https://www.aria.developpement-durable.gouv.fr/wp-content/files_mf/FD_14373_oppau_1921_ang.pdf" id="mwB-I" rel="mw:ExtLink nofollow">Archived</a> <span class="cs1-format" id="mwB-M">(PDF)</span> from the original on August 6, 2023<span class="reference-accessdate" id="mwB-Q">. Retrieved <span class="nowrap" id="mwB-U">August 6,</span> 2023</span>.</cite><span about="#mwt42" class="Z3988" id="mwB-Y" title="ctx_ver=Z39.88-2004&amp;rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&amp;rft.genre=unknown&amp;rft.jtitle=ARIA&amp;rft.atitle=French+Ministry+of+Environment%2C+Explosion+in+a+nitrogenous+fertiliser+plant%2C+ARIA+14373&amp;rft_id=https%3A%2F%2Fwww.aria.developpement-durable.gouv.fr%2Fwp-content%2Ffiles_mf%2FFD_14373_oppau_1921_ang.pdf&amp;rfr_id=info%3Asid%2Fen.wikipedia.org%3ASeptember+21"></span></span>