SHANGHAI, May 5 -- Hundreds of Chinese people attended a memorial service on Monday in Shanghai to mourn two young firefighters killed in the line of duty.

Relatives of the firefighters, Qian Lingyun and Liu Jie, broke down in tears during the event, which took place at the city's Longhua Funeral Home.

Qian and Liu, aged 23 and 20 respectively, fell to their deaths while tackling a blaze in a high-rise building on Thursday. An explosion caused them to fall from a 13th floor apartment window.

On China's Twitter-like microblogging site Weibo, thousands of netizens expressed their grief at the deaths of the "heroes", and posted images of burning candles and crying faces.

On Sunday, the Ministry of Public Security declared Qian and Liu martyrs.