An apartment building under construction in the North Korean capital of Pyongyang has collapsed, causing an unspecified number of casualties, the state media reported Sunday. The North's Korean Central News Agency (KCNA) said the accident occurred in the Pyongchon District on May 13 as "the construction of an apartment house was not done properly, and officials supervised and controlled it in an irresponsible manner."    The KCNA reported that a "state emergency mechanism" was formed to rescue survivors and treat the wounded, and senior officials met with bereaved families and citizens in the district to express "deep consolation and (issue an) apology."    Among the ranking officials were Minister of People's Security Choe Pu-il, General Officer of the Korean People's Internal Security Forces Sonu Hyong-chol and Chairman of the Pyongyang City People's Committee Cha Hui-rim.